Online research in philosophy

Galileo claimed inconsistency in the Aristotelian dogma concerning falling bodies and stated that all bodies must fall at the same rate. However, there is an empirical situation where the speeds of falling bodies are proportional to their weights; and even in vacuo all bodies do not fall at the same rate under terrestrial conditions. The reason for the deficiency of Galileo’s reasoning is analyzed, and various physical scenarios are described in which Aristotle’s claim is closer to the truth than is Galileo’s. The purpose is not to reinstate Aristotelian physics at the expense of Galileo and Newton, but rather to provide evidence in support of the verdict that empirical knowledge does not come from prior philosophy.

I begin with an explication of "thought experiment". I then clarify the role that intuitions play in thought experiments by addressing two important issues: (1) the informativeness of thought experiments and (2) the legitimacy of the method of thought experiments in philosophy and the natural sciences. I defend a naturalistic account of intuitions that provides a plausible explanation of the informativeness of thought experiments, which, in turn, allows thought experiments to be reconstructed as arguments. I also specify criteria for distinguishing bad "intuition pumps" from legitimate thought experiments. These criteria help us to avoid being seduced by the dangerous suggestive power of misleading intuitions.

At the end of the last century, Ernst Mach coined a term to describe a particular technique of scientific investigation, a mental analogue to physical experiment which he dubbed "Gedunkenexperiment."I According to Mach, this method is central to the history of science; its greatest practitioners include Aristotle and Galileo, and its careful employment "led to enormous changes in our thinking and to an opening up of most important new paths of inquiry."2 In the century that followed, Mach's term (and its English translation) showed up occasionally in the philosophy of science literature, most notably, perhaps, in Karl Popper's "On the Use and Misuse of Imaginary Experiments, Especially in Quantum Theory,"s and in Thomas Kuhn's, "A Function for Thought Experiments."4 Discussions of the technique — in science and in philosophy — made sporadic appearances on the pages of philosophy journals, each year's Philosophers' Index sporting some dozen entries under "Thought Experiment." Then, in the mid-1980s, the Zeitgeist smiled upon thought experiments; they were explicitly recognized as a central technique in analytic philosophy, and self-conscious philosophical scrutiny was directed upon them.s In the Spring of 1986, Tamara Horowitz and Gerald Massey organized a conference at the University of Pittsburgh on "The Place of Thought Experiments in Science and Philosophy." The papers given at that conference, along with several others inspired by it, are collected in Thought Experiments in Science and Philosophy, published in 1991. A year later, Roy Sorensen published his Thought Experiments, a detailed ten-chapter discussion of thought experiments in philosophy and science, in which he defends their continuity with physical experiment, and adduces numerous arguments in favor of their philosophical legitimacy. Sorensen's style is chatty and unpretensious, full of striking turns of phrase and colloquialisms: "I am bullish on the comparison;" "this protoype gives us a bum steer;" "Wittgenstein discourages fascination with mental freak shows;" "traditional metaphysicians scoffed at Meinong's....

The literature on thought experiments has been mainly concernedwith thought experiments that are directed at a theory, be it in aconstructive or a destructive manner. This has led somephilosophers to argue that all thought experiments can beformulated as arguments. The aim of this paper is to drawattention to a type of thought experiment that is not directed ata theory, but fulfills a specific function within a theory. Suchthought experiments are referred to as functional thoughtexperiments, and they are routinely used in applied statistics. An example is given from frequentist statistics, where a thoughtexperiment is required to establish the probability space. It isconcluded that (a) not all thought experiments can be formulated asarguments, and (b) the role of thought experiments is more generaland more important to scientific reasoning than has previouslybeen recognized.

Are thought experiments nothing but arguments? I argue that it is not possible to make sense of the historical trajectory of certain thought experiments if one takes them to be arguments. Einstein and Bohr disagreed about the outcome of the clock-in-the-box thought experiment, and so they reconstructed it using different arguments. This is to be expected whenever scientists disagree about a thought experiment's outcome. Since any such episode consists of two arguments but just one thought experiment, the thought experiment cannot be the arguments.

Contemplating imaginary scenarios that evoke certain sorts of quasi‐sensory intuitions may bring us to new beliefs about contingent features of the natural world. These beliefs may be produced quasi‐observationally; the presence of a mental image may play a crucial cognitive role in the formation of the belief in question. And this albeit fallible quasi‐observational belief‐forming mechanism may, in certain contexts, be sufficiently reliable to count as a source of justification. This sheds light on the central puzzle surrounding scientific thought experiment, which is how contemplation of an imaginary scenario can lead to new knowledge about contingent features of the natural world.

Arguments from thought experiment ask the reader to imagine some hypothetical, sometimes exotic, often fantastic, scenario for the sake of illustrating or countering some claim. Variously characterized as mental experimentation, imaginary cases, and even crazy cases, thought experiments figure into both scientific and philosophical arguments. They are often criticized for their fictive nature and for their lack of grounding. Nevertheless, they are common especially in arguments in ethics and philosophy of mind. Moreover, many thought experiments have spawned variations that attempt to both affirm and refute their original arguments. These emended thought experiments exhibit a variety of styles, details, and embellishments. A rhetorical analysis of these variations suggests a reciprocal influence between the arguers' selection of details and their philosophical commitments. I offer examples of this relationship from the variations on John Searle's Chinese Room thought experiment and Judith Thomson's unconscious violinist thought experiment.

This essay attempts to demonstrate that it is doubtful if Galileo's famous thought experiment concerning falling bodies in his 'Dialogues Concerning Two New Sciences' (Galileo 1954: 61-64) actually does succeed in proving that Aristotle was wrong in claiming that "bodies of different weight […] move […] with different speeds which stand to one another in the same ratio as their weights," (Galileo 1954: 61). (Part I); and further that it is likewise doubtful that that argument does or even can establish Galileo's own famous 'Law of Falling Bodies,' viz., that regardless of their weight all bodies fall with the same speed. (Part II).

My theme is thought experiment in natural science, and its relation to real experiment. I shall defend the thesis that thought experiments that do not lead to theorizing and to a real experiment are generally of much less value that those that do so. To illustrate this thesis I refer to three examples, from three very different periods, and with three very different kinds of status. The first is the classic thought experiment in which Galileo imagined that he had, by pure thought, demolished Aristoteles' dogma that heavier bodies fall more quickly than light ones. I will show that he was mistaken. The second is the Einstein-Podolsky-Rosen paper purporting to show that quantum mechanics must be incomplete in its domain of application. This thought experiment is a very good one, not because its conclusions are correct, but precisely because it was fruitful, leading to theory and, above all, to a real experiment. Finally I discuss the modern string theory of everything, which, while it is regarded as a physical theory by its instigators, shares some properties of the least successful sort of thought experiment.

The paper is a contribution to the debate on the epistemological status of thought experiments. I deal with the epistemological uniqueness of experiments in the sense of their irreducibility to other sources of justification. In particular, I criticize an influential argument for the irreducibility of thought experiments to general arguments. First, I introduce the radical empiricist theory of eliminativism, which considers thought experiments to be rhetorically modified arguments, uninteresting from the epistemological point of view. Second, I present objections to the theory, focusing on the critique of eliminativism by Tamar Szabó Gendler based on the reconstruction of famous Galileo's Pisa experiment. I show that her reconstruction is simplistic and that more elaborate reconstruction is needed for an appropriate assessment of the epistemic power of general argument. I propose such a reconstruction and demonstrate that general version of Pisa experiment is epistemically equal to the particular one. Thus, from an epistemological perspective, Galileo's thought experiment is reducible to a straightforward argument without particular premises.