Some have suggested that certain classical physical systems have undecidable long-term behavior, without specifying an appropriate notion of decidability over the reals. We introduce such a notion, decidability in (or d- ) for any measure , which is particularly appropriate for physics and in some ways more intuitive than Ko's (1991) recursive approximability (r.a.). For Lebesgue measure , d- implies r.a. Sets with positive -measure that are sufficiently "riddled" with holes are never d- but are often r.a. This explicates Sommerer (...) and Ott's (1996) claim of uncomputable behavior in a system with riddled basins of attraction. Furthermore, it clarifies speculations that the stability of the solar system (and similar systems) may be undecidable, for the invariant tori established by KAM theory form sets that are not d-. (shrink)

This study analyses the predictions of the General Theory of Relativity (GTR) against a slightly modified version of the standard central mass solution (Schwarzschild solution). It is applied to central gravity in the solar system, the Pioneer spacecraft anomalies (which GTR fails to predict correctly), and planetary orbit distances and times, etc (where GTR is thought consistent.) -/- The modified gravity equation was motivated by a theory originally called ‘TFP’ (Time Flow Physics, 2004). This is now replaced by (...) the ‘Geometric Model’, 2014 [20], which retains the same theory of gravity. This analysis is offered partially as supporting detail for the claim in [20] that the theory is realistic in the solar system and explains the Pioneer anomalies. The overall conclusion is that the model can claim to explain the Pioneer anomalies, contingent on the analysis being independently verified and duplicated of course. -/- However the interest lies beyond testing this theory. To start with, it gives us a realistic scale on which gravity might vary from the accepted theory, remain consistent with most solar-scale astronomical observations. It is found here that the modified gravity equation would appear consistent with GTR for most phenomena, but it would retard the Pioneer spacecraft by about the observed amount (15 seconds or so at time). Hence it is a possible explanation of this anomaly, which as far as I know remains unexplained now for 20 years. -/- It also shows what many philosophers of science have emphasized: the pivotal role of counterfactual reasoning. By putting forward an exact alternative solution, and working through the full explanation, we discover a surprising ‘counterfactual paradox’: the modified theory slightly weakens GTR gravity – and yet the effect is to slow down the Pioneer trajectory, making it appear as if gravity is stronger than GTR. The inference that “there must be some tiny extra force…” (Musser, 1998 [1]) is wrong: there is a second option: “…or there may be a slightly weaker form of gravity than GTR.” . (shrink)

The counterfactual account of physical computation is simple and, for the most part, very attractive. However, it is usually thought to trivialize the notion of physical computation insofar as it implies ‘limited pancomputationalism’, this being the doctrine that every deterministic physical system computes some function. Should we bite the bullet and accept limited pancomputationalism, or reject the counterfactual account as untenable? Jack Copeland would have us do neither of the above. He attempts to thread a path between the two (...) horns of the dilemma by buttressing the counterfactual account with extra conditions intended to block certain classes of deterministic physical systems from qualifying as physical computers. His theory is called the ‘algorithm execution account’. Here we show that the algorithm execution account entails limited pancomputationalism, despite Copeland’s argument to the contrary. We suggest, partly on this basis, that the counterfactual account should be accepted as it stands, pancomputationalist warts and all. (shrink)

Belief in the divine origin of the universe began to wane most markedly in the nineteenth century, when scientific accounts of creation by natural law arose to challenge traditional religious doctrines. Most of the credit - or blame - for the victory of naturalism has generally gone to Charles Darwin and the biologists who formulated theories of organic evolution. Darwinism undoubtedly played the major role, but the supporting parts played by naturalistic cosmogonies should also be acknowledged. Chief among these (...) was the nebular hypothesis proposed by Pierre Simon Laplace in 1796, which explained the origin of the solar system as a natural development over extended periods of time. Ronald Numbers focuses on Laplace's theory as it affected American scientific thought. he first traces the history of Laplace's cosmogony chronologically, from its European inception to its demise about 1900. the last three chapters explore some of the theological and scientific consequences resulting from the acceptance of this cosmogony. Most significant was the change in the status of supernatural doctrine. When the nebular hypothesis lost credence at the end of the nineteenth century, those who had before tried to accommodate natural theory with supernatural doctrine no longer felt compelled to do so when faced with succeeding theories. The nebular hypothesis, it seems, had established natural law in the heavens. (shrink)

FDE, LP and K3 are closely related to each other and admit of an intuitive informational interpretation. However, all these logics are co-NP complete, and so idealized models of how an agent can think. We address this issue by shifting to signed formulae, where the signs express imprecise values associated with two bipartitions of the corresponding set of standard values. We present proof systems whose operational rules are all linear and have only two structural branching rules that express a generalized (...) Principle of Bivalence. Each of these systems leads to defining an infinite hierarchy of tractable approximations to the respective logic, in terms of the maximum number of allowed nested applications of the two branching rules. Further, each resulting hierarchy admits of an intuitive 5-valued non-deterministic semantics. (shrink)

In a new paper in recent issue of this journal (PSTJ), Prof. M. Pitkanen describes a solar system model inspired by spiral galaxies. While we appreciate his new approach, we find it lacks substantial discussion on the nature of vortices and chirality in galaxy. Therefore we submit a viewpoint that Gross-Pitaevskii model can be a more complete description of both solar system and also spiral galaxies, especially taking into account the nature of chirality and vortices in (...) galaxies. In this article, we also hope to bring out some correspondence among existing models, so we discuss shortly: the topological vortice approach, Burgers equation in the light of KAM theory, and the Cantorian Navier-Stokes approach. Of course, this short article is far from being complete. We hope further investigation can be done around this line of approach. Aim of this paper: With this article, we hope to begin a healthy dialogue with Prof. M. Pitkanen, especially on his solar system model, since we also believe that he also support “evidence-based physics.” Limitation: In this paper we only discuss Pitkanen’s solar system model, we don’t discuss his other papers in a recent issue of PSTJ. (shrink)

A most unusual guide to the solar system, A Little Book of Coincidence suggests that there may be fundamental relationships between space, time, and life that have not yet been fully understood. From the observations of Ptolemy and Kepler to the Harmony of the Spheres and the hidden structure of the solar system, John Martineau reveals the exquisite orbital patterns of the planets and the mathematical relationships that govern them. A table shows the relative measurements of (...) each planet in eighteen categories, and three pages show the beautiful dance patterns of thirty six pairs of planets and moons. (shrink)

FDE is a logic that captures relevant entailment between implication-free formulae and admits of an intuitive informational interpretation as a 4-valued logic in which “a computer should think”. However, the logic is co-NP complete, and so an idealized model of how an agent can think. We address this issue by shifting to signed formulae where the signs express imprecise values associated with two distinct bipartitions of the set of standard 4 values. Thus, we present a proof system which consists (...) of linear operational rules and only two branching structural rules, the latter expressing a generalized rule of bivalence. This system naturally leads to defining an infinite hierarchy of tractable depth-bounded approximations to FDE. Namely, approximations in which the number of nested applications of the two branching rules is bounded. (shrink)

What is the relationship of history to the phylogenetic evolution of man? Historians, like all specialists, are wont to restrict themselves to their own problems and, therefore, do not deal with this question. Only some popular books on the history of the world cross the dividing line between social and natural science. They start with the origin of the solar system, describe the development of the crust of the earth and of life, turn to prehistoric civilization and (...) ancient Egypt, and eventually finish with the history of present times. It is striking that those expositions become more and more detailed the nearer they come to their end. Near the beginning one page describes ten million years, near the end ten months. (shrink)

The depth-bounded approach seeks to provide realistic models of reasoners. Recognizing that most useful logics are idealizations in that they are either undecidable or likely to be intractable, the approach accounts for how they can be approximated in practice by resource-bounded agents. The approach has been applied to Classical Propositional Logic (CPL), yielding a hierarchy of tractable depth-bounded approximations to that logic, which in turn has been based on a KE/KI system. -/- This Thesis shows that the approach can (...) be naturally extended to useful nonclassical logics such as First-Degree Entailment (FDE), the Logic of Paradox (LP), Strong Kleene Logic (K3 ) and Intuitionistic Propositional Logic (IPL). To do this, we introduce a KE/KI-style system for each of those logics such that: is formulated via signed formulae, consist of linear operational rules and branching structural rule(s), can be used as a direct-proof and a refutation method, and is interesting independently of the approach in that it has an exponential speed-up on its tableau system counterpart. The latter given that we introduce a new class of examples which we prove to be hard for all tableau systems sharing the V/& rules with the classical one, but easy for their analogous KE-style systems. Then we focus on showing that each of our KE/KI-style systems naturally yields a hierarchy of tractable depth-bounded approximations to the respective logic, in terms of the maximum number of allowed nested applications of the branching rule(s). The rule(s) express(es) a generalized rule of bivalence, is (are) essentially cut rule(s) and govern(s) the manipulation of virtual information, which is information that an agent does not hold but she temporarily assumes as if she held it. Intuitively, the more virtual information needs to be invoked via the branching rule(s), the harder the inference is for the agent. So, the nested application the branching rule(s) provides a sensible measure of inferential depth. We also show that each hierarchy approximating FDE, LP, and K3 , admits of a 5-valued non-deterministic semantics; whereas, paving the way for a semantical characterization of the hierarchy approximating IPL, we provide a 3-valued non-deterministic semantics for the full logic that fixes the meaning of the connectives without appealing to “structural” conditions. -/- Moreover, we show a super-polynomial lower bound for the strongest possible version of clausal tableaux on the well-known class of “truly fat” expressions (which are easy for KE), settling a problem left open in the literature. Further, we investigate a hierarchy of tractable depth-bounded approximations to CPL based only on KE. Finally, we propose a refinement of the p-simulation relation which is adequate to establish positive results about the superiority of a system over another with respect to proof-search. (shrink)

The author specifies the origin of the terms “Copernican Upheaval” and “Copernican Revolution” considering the spatial interpretations of this philosophical metaphor, which was evoked by the Kantian analogy between his model of knowledge process and the model of the solar system by Copernicus. On the base of Solomon Maimon’s criticism and subsequent scientific discussion, the author studies the analogy between a rotation of celestial bodies and the conformity of objects to knowing reason. As the result, the author (...) offers two approaches to the interpretation of the spatial analogy of the Copernican Revolution. 1) As the analogy of mobility (plasticity) and immobility (immutability) of celestial bodies / reason in relation to knowable objects. 2) As the analogy of relativity and absoluteness of movement / cognition, leads to the question of the starting point and direction of predication in cognitive trajectories. (shrink)

This piece explores the origins of science fiction in philosophical speculation about the size of the universe, the existence of other solar systems and other galaxies, and the possibility of alien life. Science fiction helps us to grapple with the dizzying possibilities that a vast universe affords, by allowing our imagination to fill in the details.

The discovery of a second genesis of life besides the one on Earth, this time on Mars, would have profound scientific and philosophical implications. Scientifically, it would provide a second example of biochemistry and of evolutionary history. Many important biological questions may be answerable through the comparison of biochemistry between the life forms on the two planets. Philosophically, the discovery of a second genesis of life in our solar system would suggest that the phenomenon of life is distributed (...) throughout the universe. We could finally be confident that we are not alone. To protect a second genesis as we search for it, the robotic and human exploration of Mars should be done in a way that is biologically reversible, i.e., we must be able to undo our contamination of Mars if we discover a second genesis of life there. It is important to note that human exploration can be done in a way that is biologically reversible. Further, the discovery of a second genesis of life on Mars poses new questions in ethics. One question is: what ethical consideration is due to an alien life form when that life is distinctly different from Earth life, and the members of that life are no more advanced than microorganisms? Will we choose to terraform Mars to enhance the richness and diversity of the indigenous life we find there? In considering our answers to these questions, we should note that for most of Earth’s history our ancestors were microscopic. (shrink)

For decades most scientists assumed that life emerged billions of years ago in a “primordial soup” somewhere on the Earth’s surface. Evidence is mounting, however, that life may have begun deep beneath the surface, perhaps near a volcanic ocean vent or even inside the hot crust itself. Since there are hints that life’s history on Earth extends back through the phase of massive cosmic bombardment, it may be that life started on Mars and came here later, perhaps inside rocks ejected (...) from the Red Planet by large impacts. The traffic of intact rocks between Mars and Earth is now an established fact, and experiments confirm that microbes could survive the rigours of the journey through space if cocooned within such material. Unfortunately, this planetary cross- contamination compromises astrobiologists’ hope of finding a second genesis in the solar system. (shrink)

A profound exploration of the simple numerical ratios that underlie our solar system, its musical harmony, and our earliest religious beliefs.

Many solar systems in the universe may be expected to contain rocky planets that have accreted organic compounds. These compounds are likely to be universally found. In addition, the chemistry of sulfur, phosphorus, and iron is likely to dominate energy transductions and monomer activation, leading to the eventual emergence of polymers. Proteins and polynucleotides provide living matter with function, structure, and information. The conceptual puzzle regarding their emergence is discussed. The fitness of various elements to serve various roles is (...) analyzed from the viewpoint of electron orbitals. Elements with d orbitals are of central importance. (shrink)

Western philosophers have traditionally concentrated on theory as the means for expressing knowledge about a variety of phenomena. This absorbing book challenges this fundamental notion by showing how objects themselves, specifically scientific instruments, can express knowledge. As he considers numerous intriguing examples, Davis Baird gives us the tools to "read" the material products of science and technology and to understand their place in culture. Making a provocative and original challenge to our conception of knowledge itself, _Thing Knowledge _demands that we (...) take a new look at theories of science and technology, knowledge, progress, and change. Baird considers a wide range of instruments, including Faraday's first electric motor, eighteenth-century mechanical models of the solar system, the cyclotron, various instruments developed by analytical chemists between 1930 and 1960, spectrometers, and more. (shrink)

Machine generated contents note: 1. Astrobiology in societal context Constance Bertka; Part I. Origin of Life: 2. Emergence and the experimental pursuit of the origin of life Robert Hazen; 3. From Aristotle to Darwin, to Freeman Dyson: changing definitions of life viewed in historical context James Strick; 4. Philosophical aspects of the origin-of-life problem: the emergence of life and the nature of science Iris Fry; 5. The origin of terrestrial life: a Christian perspective Ernan McMullin; 6. (...) The alpha and the omega: reflections on the origin and future of life from the perspective of Christian theology and ethics Celia Deane-Drummond; Part II. Extent of Life: 7. A biologist's guide to the Solar System Lynn Rothschild; 8. The quest for habitable worlds and life beyond the Solar System Carl Pilcher; 9. A historical perspective on the extent and search for life Steven J. Dick; 10. The search for extraterrestrial life: epistemology, ethics, and worldviews Mark Lupisella; 11. The implications of discovering extraterrestrial life: different searches, different issues Margaret S. Race; 12. God, evolution, and astrobiology Cynthia S. W. Crysdale; Part III. Future of Life: 13. Planetary ecosynthesis on Mars: restoration ecology and environmental ethics Christopher P. McKay; 14. The trouble with intrinsic value: an ethical primer for astrobiology Kelly C. Smith; 15. God's preferential option for life: a Christian perspective on astrobiology Richard O. Randolph; 16. Comparing stories about the origin, extent, and future of life: an Asian religious perspective Francisca Cho; Index. (shrink)

Astronomers of the first half of the nineteenth century viewed our solar system entirely differently from the way twentieth-century astronomers viewed it. In the earlier period the dominant image was of a set of planets and moons, both of which kinds of bodies were inhabited by intelligent beings comparable to humans. By the early twentieth century, science had driven these beings from every planet in our system except the Earth, leaving our solar system as more (...) or less desolate regions for the most part bereft of intelligent life. This essay traces this extinction and its relation to religious thought, noting the role played in it by Sir John Herschel and especially by William Whewell. The inverse square laws for gravitation, heat radiation, and light receive special attention, as does the question of the relevance of the Christian notions of a divine incarnation and redemption. (shrink)

Abstract Environmental and public health-focused sciences are increasingly characterised as constituting an emerging discipline—planetary medicine. From a governance perspective, the ethical components of that discipline may usefully be viewed as bestowing upon our ailing natural environment the symbolic moral status of a patient. Such components emphasise, for example, the origins and content of professional and social virtues and related ethical principles needed to promote global governance systems and policies that reduce ecological stresses and pathologies derived from human overpopulation, selfishness and (...) greed—such as pollution, loss of biodiversity, deforestation and greenhouse gas emissions, as well as provide necessary energy, water and food security. Less well explored in this context, however, is the ethics that should underpin global use of emerging technologies such as nanotechnology as forms of planetary therapeutics. Nanotechnology may be particularly important, for instance, as a mechanism for improving upon photosynthesis and engineering it into human structures for localised production of carbon-neutral hydrogen based-fuel and carbohydrate-based food and fertilizer. Artificial photosynthesis, because of its unique and widespread public and environmental benefits in this period of human history, may even be termed the moral culmination of nanotechnology, assisting this planet to move beyond the Anthropocene epoch to that of the Sustainocene. This paper explores practical steps towards planetary nanomedicine involving governance of artificial photosynthesis, including a UNESCO Universal Declaration on the Bioethics and Human Rights of Natural and Artificial Photosynthesis (Global Solar Fuels and Foods ). Content Type Journal Article Category Original Paper Pages 1-13 DOI 10.1007/s11569-012-0144-4 Authors Thomas Faunce, College of Medicine, Biology and the Environment and College of Law (joint Appointment), Australian National University, Acton, Australia Journal NanoEthics Online ISSN 1871-4765 Print ISSN 1871-4757. (shrink)

William Sharp Macleay developed the quinarian system of classification in his Horæ Entomologicæ, published in two parts in 1819 and 1821. For two decades, the quinarian system was widely discussed in Britain and influenced such naturalists as Charles Darwin, Richard Owen, and Thomas Huxley. This paper offers the first detailed account of Macleay’s development of the quinarian system. Macleay developed his system under the shaping influence of two pressures: (1) the insistence by followers of Linnaeus on (...) developing artificial systems at the expense of the natural system and (2) the apparent tension between the continuity of organic nature and the failure of linear classification schemes (which continuity seemed to require). Against what he perceived as dogmatic indolence on the part of the Linnaeans, Macleay developed a philosophy of science in which hypotheses that exceeded the available evidence should be proposed and subjected to severe tests. He also developed a novel comparative anatomical methodology, the method of variation, to aid in his search for the natural system. Using this method, he developed an intricate system that showed how organic nature could be continuous without being linear. A failure to appreciate these facets of Macleay’s thought has led to several misunderstandings of him and his work, most notably that he was an idealist. These misunderstandings are here rebutted. (shrink)

Perfectionism is a multidimensional construct with both positive and negative aspects. Recently, the concept of appearance-oriented perfectionism has been introduced, which is associated with body image dissatisfaction and weight and shape control behaviors. The Physical Appearance Perfectionism Scale is a 12-item two-factor instrument developed to assess this new dimension of perfectionism. The aim of the study is to validate the Spanish version of PAPS among a representative sample of 850 male university students in Spain. Exploratory and confirmatory factorial structure, internal (...) consistency, convergent and concurrent validity, and associated predictor variables analyses have been carried out. Results showed that the Spanish version of the PAPS maintains the original factor structure with all items and proves to be a reliable instrument. Physical appearance-oriented perfectionism is associated with general perfectionism, higher body dissatisfaction, Eating Disorders and Muscle Dysmorphia symptomatology, and compulsive exercise, particularly in the Worry about Imperfection subscale. These variables also act as predictors of physical appearance perfectionism. The use of the PAPS-S and the analysis of its subscales is recommended in the context of body image-related pathologies such as Eating Disorders and Muscle Dysmorphia. (shrink)

Here is an accurate and readable translation of a seminal article by Henri Poincaré that is a classic in the study of dynamical systems popularly called chaos theory. In an effort to understand the stability of orbits in the solar system, Poincaré applied a Hamiltonian formulation to the equations of planetary motion and studied these differential equations in the limited case of three bodies to arrive at properties of the equations' solutions, such as orbital resonances and horseshoe orbits. (...) Poincaré wrote for professional mathematicians and astronomers interested in celestial mechanics and differential equations. Contemporary historians of math or science and researchers in dynamical systems and planetary motion with an interest in the origin or history of their field will find his work fascinating. (shrink)

This essay discusses how, for Hegel, freedom can be realized in nature in a rudimentary fashion in solar systems. This solves a problem in Kant’s account of freedom, namely, the problem that Kant only gives a negative argument for why freedom is not impossible but does not give a positive account of how freedom is real. I give a novel account of Kant’s negative argument. Then, I show how, according to Hegel, solar systems can be considered as exhibiting (...) freedom in a rudimentary fashion. Finally, I lay out how Hegel systematically develops this point about the freedom of solar systems in the ‘Mechanism’-chapter of the Science of Logic. In doing so, he uses Kant’s negative argument in a ‘purified’ form to arrive at an account of an ‘intimate token-type relation’ between the planets in a solar system and the law that governs their motion. The essay as a whole provides a concrete example of how Hegel is an inheritor and radicalizer of Kant, both with respect to freedom’s reality and with respect to philosophical method. (shrink)

Resumen: La problematización de la relación entre individuo y sociedad ha atravesado la historia de las ciencias sociales. El objetivo de este escrito es mostrar la originalidad de los planteamientos de Freud sobre el tópico, a través de un análisis comparativo con las aproximaciones propias de las corrientes socioantropológicas de la escuela de Cultura y Personalidad y de la Sociología Francesa. Nuestra investigación se basó en un análisis bibliográfico tanto de algunos textos socioantropológicos claves sobre dicho debate, como de la (...) producción freudiana pertinente. La interpretación del material freudiano se organizó según tres tópicos: a) la afirmación de la determinación simbólica del síntoma, b) la borradura metodológica de la distinción individuo sociedad, y c) la teorización de una eficacia mítica, transindividual y transhistórica. Concluimos subrayando los aportes del pensamiento de Freud a la discusión: la afirmación de la determinación simbólica ofrece las condiciones para la superación de la relación de externalidad entre el polo del individuo y el de la sociedad, y el consecuente rechazo a una relación especular entre ambos.: The relation between individual and society has been a main topic across the history of social sciences. The aim of this paper is to show the originality of Sigmund Freud's ideas about the topic, through a comparative analysis with the approaches of the socio-anthropological currents of the school of Culture and Personality and of French Sociology. Our research was based on a bibliographical analysis of some key socio-anthropological texts on this debate, as well as the relevant Freudian production. The interpretation of the Freudian material was organized according to three topics: a) the affirmation of the symbolic determination of symptoms, b) the methodological erasure of the individual society distinction, and c) the theorization of a mythical, transindividual and transhistorical efficacy. We conclude by emphasizing the contributions of Freud's thought to the discussion: the affirmation of symbolic determination offers the conditions for overcoming the externality relation between the pole of the individual and that of society, and the consequent rejection of a specular relationship between the two. (shrink)

"The work realized as part of the projectproject funded by the Minister of Science and Higher Education within the program under the name "Regional Initiative of Excellence" in 2019-2022 ".

From the 1st century BC onwards followers of Plato began to systematize Plato's thought. These attempts went in various directions and were subjected to all kinds of philosophical influences, especially Aristotelian, Stoic, and Pythagorean. The result was a broad variety of Platonisms without orthodoxy. That would only change with Plotinus. This volume, being the fruit of the collaboration among leading scholars in the field, addresses a number of aspects of this period of system building with substantial contributions on Antiochus (...) and Alcinous and their relation to Stoicism; on Pythagoreanising tendencies in Platonism; on Eudorus and the tradition of commentaries on Aristotle's Categories; on the creationism of the Jewish Platonist Philo of Alexandria; on Ammonius, the Egyptian teacher of Plutarch; on Plutarch's discussion of Socrates' guardian spirit. The contributions are in English, French, Italian and German. (shrink)

The possibility of seeding other planets with life poses a tricky dilemma. On the one hand, directed panspermia might be extremely good, while, on the other, it might be extremely bad depending on what factors are taken into consideration. Therefore, we need to understand better what is ethically at stake with planetary seeding. I map out possible conditions under which humanity should spread life to other solar systems. I identify two key variables that affect the desirability of propagating life (...) throughout the galaxy. The first is axiological and depends on which value theory in environmental ethics is correct. The second is empirical and depends on whether life is common or not in our region of the universe. I also consider two ethical objections to an interplanetary life-seeding mission: the risk of interfering with indigenous life and the risk of increasing suffering in our galaxy. (shrink)

In their ‘Ethical and Technical Challenges in Compensating for Harm Due to Solar Radiation Management Geoengineering’ (2014), Toby Svoboda and Peter Irvine (S&I) argue that there are significant technical and ethical challenges that stand in the way of crafting a just solar radiation management (SRM) compensation system. My aim in this article is to contribute to the project of addressing these problems. I do so by focusing on one of S&I’s important ethical challenges, their claim that the (...) polluter pays principle (PPP) is too problematic to be useful in determining responsibility for SRM compensation. Their argument for the latter claim consists in a series of allegations, mostly in the form of questions, that are thought to indicate serious difficulties standing in the way of using the PPP to craft a just compensation system. I argue that S&I fail to substantiate these allegations: the PPP is not as problematic as S&I suggest, and moreover, is a viable candidate for determining responsibility for SRM compensation. S&I raise five allegations against the PPP. I discuss each in turn. (shrink)