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Assessing Direct and Indirect Evidence in Linguistic Research


This paper focuses on the linguistic evidence base provided by proponents of conceptualism (e.g., Chomsky) and rational realism (e.g., Katz) and challenges some of the arguments alleging that the evidence allowed by conceptualists is superior to that of rational realists. Three points support this challenge. First, neither conceptualists nor realists are in a position to offer direct evidence. This challenges the conceptualists’ claim that their evidence is inherently superior. Differences between the kinds of available indirect evidence will be discussed. Second, at least some of the empirical evidence provided by the conceptualist is flawed. It is not obtained independently of theoretical commitments, alternative interpretations have not been ruled out, and some of the thought experiments intended to extend the evidence base are conceptually flawed. Third, the widely held assumption that rational realism disallows empirical evidence relevant to linguistics is dubious. It will be shown that the limitation imposed by rational realism concerns strictly formal linguistics. The rationalist realist has no reason to impose any restriction on the evidence relevant to psycholinguistics. I conclude that it is a mistake to dismiss realism based on the assumption that it imposes undue restrictions on evidence that is relevant to linguistics.

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  1. 1.

    This view is also referred to as [linguistic] Platonism. The term ‘rational realism’ avoids the equation of Platonism with unscientific and ‘mysterious’ (e.g., Chomsky 1986a; Iten et al. 2006) and is adopted throughout. It refers strictly to the linguistic realism suggested by Katz (1998).

  2. 2.

    The rationalist realist may agree with the conceptualist that some evidence is more relevant than other for psycholinguistics. But her ontological commitment does not require her to reject psycholinguistic relevance the conceptualist considers important.

  3. 3.

    See Katz (1981, 1990, 1998, 2004), Katz and Postal (1991), Postal (2003) for defense of rational realism.

  4. 4.

    For examples see Chomsky (1975, 1980c, 1986a, 2002, 2007), Fodor (1985), Katz (1981, 1985, 1996, 1998), Katz and Postal (1991), Postal (2003, 2009), (Stainton 2006) (Iten et al. 2006).

  5. 5.

    For details see Chomsky (1986a, 2000a, 2000b, 2002, 2007).

  6. 6.

    Currently brain research relies on rather crude instruments, which give us only indirect access to brain activity fluctuations etc. But a similar limitation applies to most empirical research. We do rely on more or less sophisticated instruments that mediate between the natural phenomenon we study and our sense organs. Hence, the causal link is rarely from the phenomenon directly to our sense perception and the distinction between direct and indirect evidence seems to be one in degree not in kind.

  7. 7.

    This proposal has not been modified substantially since the 1980s and Chomsky continues to insist that I-language is genetically determined (e.g., Chomsky 2000a, 2000b, 2002, 2007, 2010).

  8. 8.

    See for example Culicover and Jackendoff (2005), Stainton (2006), Jackendoff (2007), (Iten et al. 2006).

  9. 9.

    For example Chomsky (1975, 1980a, 2007) invokes Martian Scientists, Fodor (1985) proposes creatures with infinite memories, and Stainton (2006) discusses patients with hypothetical cognitive impairments.

  10. 10.

    A proponent of this view was Quine (1960). It is not clear that currently working linguists are committed to the Quinean position described by Iten et al. (2006).

  11. 11.

    Nominalists and conceptualists disagree about which evidence is relevant (for details see (Iten et al. 2006)) but as both camps agree that only empirical evidence is relevant this dispute shall not concern us here.

  12. 12.

    This view has been proposed by Jerold J. Katz (e.g., Katz (1998, 2004)). See also Katz (1981, 1990, 1996), Katz and Postal (1991), and Postal (2003, 2009).

  13. 13.

    Seemingly there is no English term for this German expression. “Premature laurels” refers to uncritical acceptance given based on expectation not on evidence. The award of the Nobel Peace Prize to President Obama in 2009 was a recent example.

  14. 14.

    For details see Clark (2009) or any recent neuro-linguistic publications. The names and precise location of these brain areas are not relevant here. We can also ignore the still ongoing debate between proponents of strict modularity and distributed language related brain structures. What is relevant is that on any view the current technology does not allow direct access to the brain structures that are involved in language related tasks and the indirect evidence merely tells us that an area of the brain is more active during a task not how this task is performed there.

  15. 15.

    See Pullum and Scholz (2002) for a detailed account of degenerative or defective empirical evidence.

  16. 16.

    In theory the best possible evidence will investigated first. In reality researchers face financial and time constraints. Currently brain scanning is expensive and laborious. Available data have often been collected for a different purpose (e.g., locating sources for impaired linguistic capacities). Many of the available databases have been transcribed to improve ease of use; in the process data may have been compromised.

  17. 17.

    For some history on thought experiments see Brown and Fehige (2011), for critique see Wilkes (1988).

  18. 18.

    The notion of infinite short-term memories appears incoherent, so we should charitably assume Fodor meant infallible short-term memories. Even under this charitable assumption Fodor’s ‘abstraction’ does not offer any justification for the competence/performance difference, it simply presupposes it.

  19. 19.

    An almost identical version of this thought experiment is employed by (Iten et al. 2006).

  20. 20.

    The following discussion is specific to Stainton’s example. However, the conclusions drawn apply to the philosophical interpretation of scientific results in general.

  21. 21.

    This means that a case similar to the one Stainton refers to in his thought experiment has been observed, eliminating the need to rely on thought experiment evidence. The neuro-psychological facts of the observed case are open to multiple interpretations. It would lead to far afield to discuss the implications here. The interested reader may consult Valentine et al. (1996), pp. 101–103.

  22. 22.

    It is impossible to give a full account and defense of it here, for such see Katz (1990, 1998). Briefly, this philosophical account of intuitions refers to the rational faculty of reasoning and is similar to the usage of ‘intuition’ (perception of clear and distinct ideas) by Descartes.

  23. 23.

    For an example see discussion in (Iten et al. 2006), pp. 235–237. It is not the purpose of the current discussion to reply to these arguments. The aim is merely to point out that it is not justified to assimilate the commitments of the rational realist to a view she does not hold.

  24. 24.

    I am indebted to Paul Postal for providing the information summarized in this section. Complete discussion can be found in Collins and Postal (2012).

  25. 25.

    Recently leading proponents of conceptualism expressed principled doubts about our ability to give such an account (e.g., Chomsky 2010, 2012; McGilvray 2009).

  26. 26.

    The view that rational realism in linguistics does not interfere with work in psychology is also expressed here: “This [view] does not deny the feasibility of an empirical science of the [psychological states of a speaker who has knowledge of a natural language]” (Postal 2003), p. 234.

  27. 27.

    Given that generative grammar predicts an infinite set of expressions for any natural language finite human can only gather evidence of a minute subset of this language. It has been questioned whether generative linguistics is conceptually coherent but this question should not concern us here. For discussion see Katz and Postal (1991), Katz (1996), Postal (2003, 2009).

  28. 28.

    E.g., Tomasello (2003), MacWhinney (2004).

  29. 29.

    E.g., Johnson and Postal (1980).


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I wish to thank Nathaniel Goldberg, Paul Postal, the participants of the Canadian Society for Epistemology’s International Symposium on Epistemic Norms, and an anonymous reviewer for critical comments on earlier drafts. All remaining errors are mine.

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Correspondence to Christina Behme.

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Behme, C. Assessing Direct and Indirect Evidence in Linguistic Research. Topoi 33, 373–383 (2014).

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  • Linguistic evidence
  • Empirical evidence
  • Direct evidence
  • Thought experiments as source of evidence
  • Conceptualism
  • Rational realism