Metaphysics is one of the broadest branches in philosophy, with questions about the nature of the world, with sub-branches within it such as ontology, epistemology and more.

I'd like to ask a question that's sort of meta-metaphysical. Metaphysics is usually (if not always) speculative: idealism-materialism, God, origin of the universe, space-time, and more subjects of interest to metaphysics which are almost always taken as speculative ideas, with outlash against it being too speculative and not connected to reality (ironic), or worse - that it doesn't have any real results or it can't ever be tested, and more comments like these.

I've heard here (from @Conifold) that metaphysics might be considered as an incubator for scientific theories, which is interesting take on it (especially when, to my knowledge, this wasn't how metaphysics was treated most of the history of philosophy), but could be helpful for the question - assuming this is true and metaphysics is an incubator for scientific theories, when does the metaphysical analysis "enough" to be taken into "action"- incorporated into a scientific theory? Is it just something that's always out there, a blend of ideas waiting to be brought to science?

In other words (though it's an entirely different take on the question) - does metaphysical analysis justifies itself on its own, or is it always to be considered as a starting point for science? And if it is really only a starting point, why would we have philosophers that'd explore metaphysics on its own and not only let scientists approach it when needed to their theories (if it isn't already the case, I'm not sure about that, but we still got philosophers like Thomas Nagel who is first and foremost a philosopher, and he talks about metaphysics)? And this, in other words, means - is metaphysics as a philosophical branch (and I'm talking practically, in the Academia) dead, and only approached from within science departments? (Note that this paragraph talks about a different topic, but a topic that's derived from the questions from the previous paragraph.)


When talking about metaphysics here, I mean metaphysics in relation to science, obviously not the metaphysics that talk about art, politics, etc.

  • What I said was that metaphysics can be an incubator of scientific theories, among many other things, it can also be invoked in art, ethics, law, politics and the rest of the culture. In a similar vein mathematics can be considered an aid to natural sciences, or even incubator of some theories, which does not preclude other uses, including for its own sake. So answers to the last paragraph are all negative. It is unclear what "when does the metaphysical analysis "enough" to be taken into "action"" means, "when" in what terms? There is no general recipe for turning speculations into theories.
    – Conifold
    Mar 21, 2018 at 23:26
  • @Conifold I'll edit that I mean metaphysics only in relation to science. An example to a "when" is what Jo Wehler proposed in his answer. Mar 22, 2018 at 7:49
  • Metaphysics is a science of logic and the idea that it produces no results is demonstrably false. Rather, it's results are studiously ignored for the sake of ideas like materialism and commonplace theism. Bradley calls it 'an antidote for dogmatic superstition' and this would be my view. It does not act as an incubator for scientific theories at this time but hopefully it might in the future. At this time it is almost entirely ignored by science and 'scientific' consciousness studies, not understood and belittled as useless. This is why you have such a low opinion of it.
    – user20253
    Mar 22, 2018 at 10:22
  • @PeterJ I just want to note on the personal level that I stand more on your side than on the side I presented in the question - I don't have low opinion of metaphysics, in fact I have very high opinion of it; I just want to understand current opinions on it, as to my knowledge this kind of views (that "belittle" metaphysics, although it doesn't necessarily belittle but instead give it a specific task) arose in the late 19th century (mainly with the rise of positivism), so I'm just trying to understand what happened. Mar 22, 2018 at 10:43
  • Pardon me YW, I do tend to bang on a bit as you know. For an astonishing but common assessment of metaphysics see the preface to the current 'Blackwell Guide to Metaphysics'. The opinion expressed there is a low as it could ever be and yet quite widespread. . .
    – user20253
    Mar 26, 2018 at 8:00

2 Answers 2


I only try to answer your headline question:

When does metaphysics stop being speculation?

According to the philosophy of Critical Rationalism, metaphysics stops being speculation exactly at the point when its speculations become testable.

Testable means that we can confirm or falsify the metaphysical thesis. Note: To confirm does not mean to prove.

  • Could you give an example? This seems to follow well with a certain aspect of what Conifold suggests, that metaphysics is an incubator for scientific theories (that when those metaphysical theories become testable it becomes a scientific theory). Mar 21, 2018 at 16:19
  • Metaphysical statements about space and time loose their speculative state when space and time combine to the physical concept of spacetime. The latter concept is part of the Special and the General Theory of Relativity.
    – Jo Wehler
    Mar 21, 2018 at 16:42
  • would it still be considered metaphysical theory, or would it be considered scientific theory? Mar 21, 2018 at 16:44
  • "Spacetime" is a concept of the scientific theories from Relativity. Nevertheless, many philosophers continue with metaphysical speculations about two independent concepts "space" and "time". The example shows how metaphysical concepts can change when they loose their speculative character.
    – Jo Wehler
    Mar 21, 2018 at 17:15

David Deutsch argues that epistemology, theory of knowledge, is an essential pillar to our understanding of the world. Specifically (from Wikipedia) :

Karl Popper's epistemology, especially its anti-inductivism and its requiring a realist (non-instrumental) interpretation of scientific theories, and its emphasis on taking seriously those bold conjectures that resist falsification.

Not exactly metaphysics as it's normally presented, but in the ball park.

There is something important about science which is not often emphasised. It is participatory. Anyone can learn the methods, take up a specialism, and contribute. Citizen science is within everyone's reach, as well as all kinds of other projects & research areas. People present science as the big ideas, the four fundamental forces, big bang cosmology, abiogenesis, interstellar travel, but they are not it. Metaphysics has been overwhelmingly focused on big theories of big thinkers, and as concerns have changed those theories have largely been mothballed, not updated and taken up by people to solve problems.

Now, I am not advocating instrumentalist metaphysics. But, I think crucial to philosophy is how it acts in our own lives, how it is a participatory practice, not a museum of ideas. Most metaphysical speculations don't solve problems people have any more.

Science alone has no interest in solving problems of people's inner lives, and I feel we are in era when the spotlight will be increasingly thrown onto those questions science cannot answer. Whether it's a rejection of reductionism like Deutsch or 'neometaphysics' of increasingly untestable string theories, metaphysics will need to catch up. We cannot be fully rounded beings, by science alone.

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