Considering that physics used to be called Natural Philosophy. But then it became a "science" once there were numerical predictions and tests.

Also when you look at Russell's theory of logic and Theory of Types, that was a philosophical topic until the invention of computers to enact his theories and it became computer science.

Or Aristotle's musings on consciousness and the mind where merely philosophy. But then along came Artificial Intelligence and now the Theory of Mind is more of a science.

Another one might be ancient philosophers considering the start of the Universe. Now that is firmly in the science field as one can measure the Cosmic Background Radiation of the Big Bang.

So does this mean that a pure philosophy are ideas that can't be tested (yet) or that no known tests exist?

What other ideas from antiquity were considered purely philosophical but which are now considered science?

  • Considering physics used to be... but a part philosophy may not have fully let go of this baby! Generally a part called metaphysics. This book, Quintin Smith et al may suggest something to you. filosofia.unimi.it/zucchi/NuoviFile/SmithOaklander95.pdf – Gordon Jul 14 '18 at 8:32
  • Here would be a NeoThomist approach, "Philosophy of Nature" by Jacques Maritain. Philosophical Library, Pub. In this book when "idealism" is spoken of, they mean Kant's Critique of Pure Reason. Anyway, there is contemporary metaphysics also. All this may be a detour not worth your time. You can also take Philosophy of Science at college, or read about it on your own. – Gordon Jul 14 '18 at 8:40
  • The difference between science and philosophy is exactly the one you stated. But philosophy is questioning and answering those untestable things which can be answered in yes/no perspective. That is a difference between arts and philosophy. – rus9384 Jul 15 '18 at 17:41
  • Not a duplicate, but might be interesting for the OP - philosophy.stackexchange.com/q/49192/30235 – Yechiam Weiss Jul 16 '18 at 3:40

No, logic and mathematics are testable (internally) but are actually prior to science rather than being included within science. It is incorrect to imagine that science is superior to philosophy; it would be more correct to imagine science as one philosophy among others, with science-ism, i.e. the only true knowledge is scientific, nearby.

  • I don't mean science is superior. I just mean a philosophy has an additional classification as a science when there are testable predictions. Also, mathematics can't really be proved to be self consistent according to Godel. – zooby Jul 14 '18 at 4:09
  • Didn't know about that from Godel! Maybe that means you're right--- but then that makes sense because "testable" and "science" go together pretty well. – elliot svensson Jul 14 '18 at 4:13
  • Logical self consistency is not the same as testability. To test in the science sense requires that the theory make predictions about experience, and then these predictions be compared to experience. This is very different to logic. You do not determine the truth of [if A implies B, and B implies C then A implies C] by examining objects or observing behavior. – user34017 Sep 13 '18 at 17:15

From philosophy to science - science disconnects from philosophy

One way of reading the history of philosophy is to see it as the progressive detachment of inquiries, once encompassed in philosophy, from the parent subject to form separate, independent inquiries. This happened to physics, to psychology, to linguistics, even to geology, geography, and meteorology. These new subjects support, as distinct from philosophy as ordinarily understood, specialist and often highly technical vocabularies, laws, counterfactuals, equations, hypotheses, predictions and retrodictions and crucially experiments. Not all of these are completely missing from philosophy but the new offspring incorporate and sophisticate them to a much higher degree than philosophy now does or ever did. Once an inquiry acquires a sufficient set of such features, it ceases to be a part of philosophy. ('Sufficient' is unavoidably vague and it is not for philosophy to decide what is sufficient.)

From philosophy back to science - philosophy reconnects with science

Philosophy itself has changed, and not just by the loss of the new sciences. In the 1950s and 60s there was a widespread view of philosophy as conceptual analysis, the kind of activity that could be conducted in an armchair and required no specialist knowledge. Philosophy hived itself off in a kind of self-exile from experimental science. This is no longer the case as Kwame Anthony Appiah explains :

There are all kinds of ways in which experimentation has been brought to bear in our discipline. For decades, of course, philosophers of mind have been working closely with their peers in psychology and psycholinguistics and computer science; there has been an effort to ground the philosophy of language, too, in more naturalistic theories of the mind (an effort to which my first two books belong). Philosophers who work on consciousness can tell you all about Capgras Syndrome and research in various forms of neurologically induced agnosia.

The relevance of empirical research tends to be more hotly contested in the obviously normative reaches of moral theory. But here, too, the "renewed incursions" have been hard to miss. Over the past decade, for instance, there's been a debate between virtue ethicists and critics armed with findings from social psychology?in particular, empirical evidence for what's called "situationism." These critics draw on decades of research suggesting that much of what people do is best explained not by traits of character but by systematic human tendencies to respond to features of their situations that nobody previously thought to be crucial at all.18

Situationists think that someone who is, say, reliably honest in one kind of situation will often be reliably dishonest in another. Back in 1972, experimental psychologists had found that, if you dropped your papers outside a phone booth in a shopping mall, you were far more likely to be helped by someone who had just had the good fortune of finding a dime waiting for them in the return slot. Ayear later, John Darley and Daniel Batson discovered?this is probably the most famous of these experiments?that Princeton seminary students, even those who had just been reflecting on the Gospel account of the Good Samaritan, were much less likely to stop to help someone "slumped in a doorway, apparently in some sort of distress," if they'd been told that they were late for an appointment. More recently, experiments showed that you were more likely to get change for a dollar outside a fragrant bakery shop than standing near a "neutral smelling dry-goods store."

Many of these effects are extremely powerful: huge differences in behavior flow from differences in circumstances that seem of little or no normative consequence. Putting the dime in the slot in that shopping mall raised the proportion of those who helped pick up the papers from 1 out of 25 to 6 out of 7; i.e., from almost no one to almost everyone. Seminarians in a hurry are six times less likely to stop like a Good Samaritan.20 Knowing what I've just told you, you should surely be a little less confident that "she's helpful" is a good explanation next time someone stops to assist you in picking up your papers, especially if you're outside a bakery!

Philosophers inspired by situationists have argued that this reality is at odds with the conception of human character that underlies virtue ethics. For when virtue ethicists ask us to be virtuous, they typically mean that we should have, or cultivate, persistent, multitrack dispositions to, say, act compassionately, or honestly. Their situationist critics object that we're simply not built that way?that character, as the virtue ethicists conceive it, is about as real as phlogiston. Crudely put: If there's no such thing as character, then the project of a character ethics?a morality centered on virtues? is a waste of time.


In recent years, however, philosophers have done more than draw upon research by experimentalists in other disciplines. The recent currency of the phrase "experimental philosophy" often refers to research that, in the mold of Arne Naess, has actually been conducted by philosophers.. .often, as with Naess, on nonphilosophers. Much of this work is in a continuation of the project of conceptual analysis.24 If conceptual analysis is the analysis of "our" concepts, then shouldn't one see how "we"?or representative samples of us?actually mobilize concepts in our talk? So one strain of this work seeks to elicit and tabulate intuitions people have about various scenarios.

The use of such scenarios, or thought experiments, is a hallmark of philosophy. Yet the newer philosophical experimentalists seem to have noticed that many thought experiments in philosophy were, so to speak, at a double remove from reality. Not only were the scenarios unrealized, the claims about how we would respond to those scenarios were also simply asserted, rather than demonstrated.

Recall Hume's Missing Shade of Blue argument. If a man had never encountered a particular shade of blue, and is now presented with a sequence of deepening shades, absent that one, will he notice the gap and be able to imagine the unseen shade? Hume, the great empiricist, writes, "I believe there are few but will be of opinion that he can." That has been the usual protocol. We conjure a scenario, and then announce that, in such case, "it would be natural to say" X, Y, or Z. (In the empirical spirit, I should report that, when I typed the phrase "it would be natural to say" into Google's Book Search, it happily returned, as its top search results, passages by Gilbert Ryle, Peter Strawson, Max Black, and Bertrand Russell.)

Most thought experiments are unrealized for good reasons. With the stroke of a pen, Frank Jackson can summon up in imagination Mary, the scientist raised in a world without color. Actually raising such a scientist, however, would be arduous, time consuming, and costly ... and likely to get bogged down in human subjects review committees. Any attempt to reproduce Judith Jarvis Thompson's thought experiment about the comatose violinist would run into protests from the musician's union. Yet the other part?finding out what people would think when contemplating such scenarios?can be expeditiously and inexpensively done. So why not remove at least some of the thought from our thought experiments? (Kwame Anthony Appiah, 'Experimental Philosophy', Proceedings and Addresses of the American Philosophical Association, Vol. 82, No. 2 (Nov., 2008), pp. 7-22 : 13-16.


Kwame Anthony Appiah, 'Experimental Philosophy', Proceedings and Addresses of the American Philosophical Association, Vol. 82, No. 2 (Nov., 2008), pp. 7-22.

W.V.O. Quine, "Epistemology Naturalized." In Ontological Relativity and Other Essays (New York: Columbia University Press, 1969), 82-83.

Timothy Williamson. "Armchair Philosophy, Metaphysical Modality and Counterfactual Thinking" (Presidential Address). Proceedings of the Aristotelian Society 105, 1 (2005): 123.


This is an interesting question and touches on the demarcation problem of science as well as the historical account of the relationship between philosophy and science. Historically, it seems the specialized branches of philosophy get their own department when they reach a particular level of success, with psychology being the most recent case.

I don't think testability plays into it as much since much of what's considered science is untestable (although it should!).

  • Could you explain why you think that "much of what's considered science is untestable"? That is at best a controversial statement (I'd consider it flatly wrong), and you're basing much of your case on it. – David Thornley Aug 15 '18 at 17:44
  • i think Popper disagrees with you, njspeer, about what demarcates science from non-science. Popper would not consider something untestable (which is not the same as "not yet tested") to be "science". testability is what is behind falsifiability. and Popper's demarcation is all about falsifiability. – robert bristow-johnson Sep 14 '18 at 3:04
  • @DavidThornley Maybe the confusion from my comment is coming from the word 'considered.' What I meant was what society commonly calls 'science.' I personally think that science should be restricted to theories that are experimentally testable. Unfortunately, that is a minority opinion. – njspeer Nov 8 '18 at 4:39

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