Infinite Monkeys and old Gedankenexperimente

Before reading this, check out the Infinite Monkey Theorem here. By the way, isn't that the coolest name for a band?

Rescher, N. (1991). Thought experimentation in pre-Socratic philosophy. In T. Horowitz & M. Gerald (Eds.) Thought experiments in science and philosophy (pp. 31-41). Lanham, MD: Rowman & Littlefield

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For Rescher, a “thought experiment” is an attempt to draw instruction from a process of hypothetical reasoning that proceeds by eliciting the consequences of a hypothesis (p. 31). As the editors observe in the introduction of the volume, this eventually amounts to identifying, rather loosely, thought experimentation and the use of assumptions – whether one knows these assumptions to be true or false.

In natural science, thought experiments are common: e.g Einstein’s pondering the question of what the world would look like if one were to travel along a lay of light (i.e. with the exact same speed). However, regardless of the definition, the idea behind thought experiments is suspicious, and has been suspicious at least since Thomas Kuhn’s “paradox of thought experiments”: the puzzling fact that thought experiment have novel empirical import even though they are conducted entirely inside one’s head.


Rescher identifies several modes of reasoning that can be regarded as thought-experimental. First of them is explanatory and functions along these lines: “X is hard to account for, but if we assume that P, which we certainly don’t know but which is not inherently implausible, then we obtain a perfectly good explanation of X” Examples are given. One subtype of this, is the use of analogy in explanatory reasoning. Example from Aristotle: The Earth is in the centre. Why? Well, in vortices, things tend to the center. Therefore, if the world would be as a vortex, that would explain why the Earth is in the centre. (This might be restated in an argumentative form, e.g. “X is the case, since …”)
Rescher considers the following two modes of thought experimentation as different: negatively demonstrative reasoning and reduction ad absurdum. In NDR, the process is as follows: Assume (TE) not-P. Deduce Q. Observe that Q is false. Maintain P. In reduction, the process is as follows: Assume (TE) not-P. Deduce P. Observe contradiction. Maintain P. Are they that different?

A fourth method, Sceptical Thought Experiment, is instantiated by Xenophanes’ famous saying: “But if cattle and horses or lions had hands, or could draw with their hands and do the works that man can do, then horses would draw the forms of the gods like horses, cattle like cattle, and they would make their bodies such as they each had themselves”. In Rescher’s re-statement: We accept P. But suppose (TE) X as a state of affairs. Then we would not accept P at all, but rather P’. Hence, we aren’t really warranted in accepting P. There is also this shorter version, attributed to Xenophanes too: “If god had not made yellow honey, men would consider figs far sweeter”

Yet a fifth method. Suppose (TE) someone did X. Then, he is an F. But Y is just like X, in F-relevant regards. Therefore, someone who does Y is F (too). I fail to see the difference between this and method number 1 (the vortex example). A sixth method is described.

The article, Rescher claims, should be seen as part of the history of modes of reasoning. But what is the principle of distinguishing these modes, at least in his article, is not apparent at all.