In this commentary I have extended the refreshing account given by Jacob, who presents Grice’s individual account of meaning and assesses its plausibility with regard to communication and knowledge transmission. I defended the view that one promising way to talk about testimony as a source of knowledge is offered by Lackey’s dualism. Here, both speaker and hearer are the important in knowledge transmission. In order to secure this transmission, the speaker has to utter a true sentence and the hearer has to check the speaker’s trustworthiness. I distinguished two kinds of personal attack:
(i) The local ad hominem argument, which is not fallacious, focuses on the proposition and personal properties of the speaker, and is a content-related, relevance-based attack based upon one’s subjective probabilistic estimation of the speaker’s reliability, which can be calculated in Bayes’ Theorem.
(ii) The global ad hominem argument, which is fallacious, is an extreme prejudice that denies that the speaker is reliable in any case. It is not usable as a tool for knowledge transmission, because it violates the stipulation of the Bayesian argumentation in which one should include some evidence in the subjective probability estimation. This extreme kind of a personal attack could be racism or stigmatizing, for instance.
(iii) Here I argued—in agreement with Jacob—that the Gricean account of mindreading is more plausible than Millikan’s account of direct perception. To use the inductive model of reasoning when evaluating a speaker’s reliability, one also has to rely on the use of belief-desire psychology. It is important to infer the intentions of the speaker, and to think about whether she has good reasons or a general propensity to speak the truth. Millikan’s framework of direct perception does not account for this, because the direct perceptibility of some abstract cases of testimony and their evaluated reliability is very implausible.
(iv) Last, I argued that the description of speaker and hearer as cooperative devices is implausible, too. First, we know that the speaker could have deceptive intentions. Second, if somebody is committing a global ad hominem attack, the interests of the utterer and her addressee fall apart. Nonetheless, the communicative intention still holds. Both parties communicate successfully, even if the hearer does not gain a new belief. So we could conclude with Grice and Sperber and Wilson that the communicative intention is sufficient for a successful communication. If the addressee commits an ad hominem fallacy, the proper function is unfulfilled. But in this case the conventional speaker action, which is part of successful communication, has been violated. I have argued that the Gricean account could well explain our communicative practices regarding epistemic contexts.
In terms of future research, it would be very interesting to see, how the Gricean philosophy of a speaker’s individual meaning and mindreading could be embedded in theories about social cognition, social epistemology and informal logics. Jacob has presented an illuminating account of how the Gricean philosophy could be embedded in modern philosophy of mind and the cognitive sciences. I propose that one should further reflect on Jacob’s arguments and adopt his conceptual framework, which I think is very precise and explanatorily fruitful. But for my own proposal of a distinction between local and global ad hominem attacks, it will be important to flesh out these accounts with regard to Bayesian reasoning and argumentation in epistemic contexts. A good candidate for elaborating this kind of research is the recent account of predictive processing, which is also based on Bayesian probabilities.
In this commentary I have claimed that these personal attacks are inductive mechanisms. But much more could be said about their functionality or even their instantiation in a cognitive system. Then it would be interesting to see if non-human cognitive systems could commit these kinds of ad hominem attacks. How precise could they be in evaluating a speaker’s reliability? Are instances of ad hominem attacks bound to a specific type of brain through which the relevant representational and functional architectures are realized? How could such a phenomenon like the global and local ad hominem attack evolve in homo sapiens, and what are the deeper underlying cognitive mechanisms of such attacks? These questions need to be answered if we want to understand these important mechanisms and processes of social knowledge, as well as our communicative society as a whole.
Acknowledgements
First of all, I am appreciative for the illuminating target paper. In addition to that, I would like to thank the two anonymous reviewers and Thomas Metzinger and Jennifer M. Windt for their editorial reviews. They really helped to improve this paper. I am also grateful to Thomas Metzinger and Jennifer M. Windt for the opportunity to contribute to this project.