Online research in philosophy

Abstract The Duhem?Quine thesis is generally presented as the radical underdetermi? nation of a theory by experimental evidence. But there is a much?neglected second aspect, i.e. the coherence or interrelatedness of the conceptual components of a theory. Although both Duhem and Quine recognised this aspect, they failed to see its consequences: it militates against the idea of radical underdetermination. Because scientific theories are coherent conceptual systems, empirical evidence penetrates, as it were, the periphery and allows the localisation of central, not just peripheral hypotheses. There is then no reason to deny the existence of crucial experiments. Both these ideas are denied in the Quine?Duhem thesis. A discussion of the famous Stem?Gerlach experiment and the role of fundamental physical constants shows, however, that localisation is not only possible but essential for the validity of scientific theories. Quine's famous ?latitude of choice? turns out to be severely restricted.

Space is big. It is very, very big. On the currently most favored cosmological theories, we are living in an infinite world, a world that contains an infinite number of planets, stars, galaxies, and black holes. This is an implication of most “multiverse theoriesâ€, according to which our universe is just one in a vast ensemble of physically real universes. But it is also a consequence of the standard Big Bang cosmology, if combined with the assumption that our universe is open or flat, as recent evidence suggests it is. An open or flat universe – assuming the simplest topology[1] – is spatially infinite at any time and contains infinitely many planets etc.

The first part of this paper discusses Quine’s views on underdetermination of theory by evidence, and the indeterminacy of translation, or meaning, in relation to certain physical theories. The underdetermination thesis says different theories can be supported by the same evidence, and the indeterminacy thesis says the same component of a theory that is underdetermined by evidence is also meaning indeterminate. A few examples of underdetermination and meaning indeterminacy are given in the text. In the second part of the paper, Quine’s scientific realism is discussed briefly, along with some of the difficulties encountered when considering the ‘truth’ of different empirically equivalent theories. It is concluded that the difference between underdetermination and indeterminacy, while significant, is not as great as Quine claims. It just means that after we have chosen a framework theory, from a number of empirically equivalent ones, we still have further choices along two different dimensions.

Research at the nanoscale (10 7 to 10 9 meters) raises a number of intriguing philosophical issues. In this paper, I address one of them: the role of what can be called “visual evidence” in the construction and assessment of nanophenomena. First, a clarification is in order regarding the concepts of visual evidence and nanophenomena. It might be thought that the former expresses a redundancy whereas the latter is an oxymoron. After all, at least if we follow its Latin etymology, evidence emerges from what is obvious to the eye (and thus can be seen). In this sense, any evidence should then be visual. However, once the concept of evidence is formulated in the context of certain philosophical views, this immediate link to a visual experience need not be maintained although, ultimately, there will always be such a link. Having said that, breaking the link with the observable is precisely what happens in the case of some of the most influential models of evidence. Rather than keeping a close link to what can be visually perceived, these models stress the way in which evidence supports certain theories in particular, by making more likely that such theories be true. With regard to “nanophenomena”, it may be argued that the word “phenomena”, at least etymologically, stands for what appears, what can be seen. And if we restrict what can be seen to what can be seen without the use of instruments (such as various kinds of microscopes), then simply nothing at the nanoscale could be literally seen. Nanophenomena turn out to be an impossibility. However, once again, if phenomena are understood in the context of certain philosophical conceptions, they need not be tied directly only to what literally appears to our unaided eyes. Phenomena may stand for a certain cluster of events that are stable and regular enough to require some kind of explanation by our theories. Clearly, phenomena will involve something that can be seen: the items with respect to which our theories will be taken to be empirically adequate or not..

If we are to constrain our place in the world, two principles are often appealed to in science. According to the Copernican Principle, we do not occupy a privileged position within the Universe. The Cosmological Principle, on the other hand, says that our observations would roughly be the same, if we were located at any other place in the Universe. In our paper we analyze these principles from a logical and philosophical point of view. We show how they are related, how they can be supported and what use is made of them. Our main results are: 1. There is a logical gap between both principles insofar as the Cosmological Principle is significantly stronger than the Copernican Principle. 2. A step that is often taken for establishing the Cosmological Principle on the base of the Copernican Principle and observations is not incontestable as it stands, but can be supplemented with a different argument. 3. The Cosmological Principle might be crucial for cosmology to the extent it is not supported by empirical evidence.

There is sufficient evidence at present to justify the belief that the universe began to exist without being caused to do so. This evidence includes the Hawking-Penrose singularity theorems that are based on Einstein's General Theory of Relativity, and the recently introduced Quantum Cosmological Models of the early universe. The singularity theorems lead to an explication of the beginning of the universe that involves the notion of a Big Bang singularity, and the Quantum Cosmological Models represent the beginning largely in terms of the notion of a vacuum fluctuation. Theories that represent the universe as infinitely old or as caused to begin are shown to be at odds with or at least unsupported by these and other current cosmological notions.

Mathematical physicist Lee Smolin has proposed a theory of Cosmological natural selection which, he argues, explains the existence of our life-supporting universe, and which, he claims, is superior to Anthropic Principle explanations. I will argue in this paper that the theory of Cosmological natural selection does not provide an improvement upon the Weak Anthropic Principle.

It is no secret that scientists argue. They argue about theories. But even more, they argue about the evidence for theories. Is the evidence itself trustworthy? This is a bit surprising from the perspective of traditional empiricist accounts of scientific methodology according to which the evidence for scientific theories stems from observation, especially observation with the naked eye. These accounts portray the testing of scientific theories as a matter of comparing the predictions of the theory with the data generated by these observations, which are taken to provide an objective link to reality.

If cosmology is to obtain knowledge about the whole universe, it faces an underdetermination problem: Alternative space-time models are compatible with our evidence. The problem can be avoided though, if there are good reasons to adopt the Cosmological Principle (CP), because, assuming the principle, one can confine oneself to the small class of homogeneous and isotropic space-time models. The aim of this paper is to ask whether there are good reasons to adopt the Cosmological Principle in order to avoid underdetermination in cosmology. Various strategies to justify the CP are examined. For instance, arguments to the effect that the truth of the CP follows generically from a large set of initial conditions; an inference to the best explanation; and an inductive strategy are assessed. I conclude that a convincing justification of the CP has not yet been established, but this claim is contingent on a number of results that may have to be revised in the future.

Current cosmological theories say that the world is so big that all possible observations are in fact made. But then, how can such theories be tested? What could count as negative evidence? To answer that, we need to consider observation selection effects.