It starts from a small set of self-evident axioms together with relevant definitions and tries to deduce a great variety of theorems from this basis, thereby mirroring the methods found in geometry.
[10] For example, many philosophers have rejected the claim of self-evidence concerning one of René Descartes's first principles stating that "he can know that whatever he perceives clearly and distinctly is true only if he first knows that God exists and is not a deceiver".
The phenomenological method can also be seen as a reaction to methodological skepticism since its defenders traditionally claimed that it could lead to absolute certainty and thereby help philosophy achieve the status of a rigorous science.
[23] A different objection to the method of phenomenological reduction holds that it involves an artificial stance that gives too much emphasis on the theoretical attitude at the expense of feeling and practical concerns.
[25][26][27] The method of verificationism consists in understanding sentences by analyzing their characteristic conditions of verification, i.e. by determining which empirical observations would prove them to be true.
While this approach has become more popular in recent years, it has also been criticized based on the argument that it tends to change the subject rather than resolve the original problem.
This often takes the form of criticism directed against theories whose premises or conclusions are very far removed from how the average person thinks about the issue in question.
[47] For example, Albert Einstein's theory of relativity constitutes a radical departure from the common-sense conception of space and time, and quantum physics poses equally serious problems to how we tend to think about how elementary particles behave.
But such a shift in the burden of proof does not constitute a blind belief in common sense since it leaves open the possibility that, for various issues, there is decisive evidence against the common-sense opinion.
[54][3] Other types take more positive approaches by defending and justifying philosophical claims, for example, based on what sounds insightful or odd to the average English speaker.
[10] This significantly complicates ordinary language philosophy, since philosophers have to take the specific context of the expression into account, which may considerably alter its meaning.
[61][62] In some cases, the imagined scenario is physically possible but it would not be feasible to make an actual experiment due to the costs, negative consequences, or technological limitations.
[10] One problem with intuitions in general and thought experiments in particular consists in assessing their epistemological status, i.e. whether, how much, and in which circumstances they provide justification in comparison to other sources of knowledge.
[71] This does not imply that all the evidence has really been considered, but it is tied to the impression that engaging in further inquiry is unlikely to make one change one's mind, i.e. that one has reached a stable equilibrium.
[70][71] The philosophical method of reflective equilibrium aims at reaching this type of state by mentally going back and forth between all relevant beliefs and intuitions.
[70][71] In this wide sense, reflective equilibrium is connected to a form of coherentism about epistemological justification and is thereby opposed to foundationalist attempts at finding a small set of fixed and unrevisable beliefs from which to build one's philosophical theory.
[70][72] One problem with this wide conception of the reflective equilibrium is that it seems trivial: it is a truism that the rational thing to do is to consider all the evidence before making up one's mind and to strive towards building a coherent perspective.
[74] Pragmatists approach intractable philosophical disputes in a down-to-earth fashion by asking about the concrete consequences associated, for example, with whether an abstract metaphysical theory is true or false.
[75] Another goal of this approach is to expose pseudo-problems, which involve a merely verbal disagreement without any genuine difference on the level of the consequences between the competing standpoints.
[80][81][82] For example, it has been used to argue for the existence of an external world based on the premise that the experience of the temporal order of our mental states would not be possible otherwise.
So in the example above, critics can argue against the transcendental argument by denying the claim that an external world is necessary for the experience of the temporal order of our mental states.
[84][85] One problem for both the positive and the negative approaches is that the data obtained from surveys do not constitute hard empirical evidence since they do not directly express the intuitions of the participants.
[91] Various other types of methods were discussed in ancient Greek philosophy, like analysis, synthesis, dialectics, demonstration, definition, and reduction to absurdity.
According to the method of epistemic conservatism, we should, all other things being equal, prefer the theory which, among its competitors, is the most conservative, i.e. the one closest to the beliefs we currently hold.
[96][10][97][98] In philosophy, the term "genealogical method" refers to a form of criticism that tries to expose commonly held beliefs by uncovering their historical origin and function.
[99][100][101] For example, it may be used to reject specific moral claims or the status of truth by giving a concrete historical reconstruction of how their development was contingent on power relations in society.
In some cases, such discoveries led the involved philosophers to overly optimistic outlooks, seeing them as historic breakthroughs that would dissolve all previous disagreements in philosophy.
One important difference is that philosophy does not use experimental data obtained through measuring equipment like telescopes or cloud chambers to justify its claims.
[9][11][43][7] For example, even philosophical naturalists emphasizing the close relation between philosophy and the sciences mostly practice a form of armchair theorizing instead of gathering empirical data.
An additional complication concerning testimony is that different philosophers often defend mutually incompatible claims, which poses the challenge of how to select between them.