The Routledge Companion to Thought Experiments
It is not news that we often make discoveries or find reasons for a mathematical proposition by thinking alone. But does any of this thinking count as conducting a thought experiment? The answer to that question is “yes,” but without refinement the question is uninteresting. Suppose you want to know whether the equation [8x + 12y = 6] has a solution in the integers. You might mentally substitute some integer values for the variables and calculate. In that case you would be mentally trying something out, experimenting with particular integer values, in order to test the hypothesis that the equation has no solution in the integers. Not getting a solution the first time, you might repeat the thought experiment with different integer inputs.