οἷον τῇ τῶν ἀφροδισίων· οὐδένα γὰρ ἂν δύνασθαι νοῆσαί τι ἐν αὐτῇ. (1152b17–18)
(… as with the pleasure of sex: no one could have any thoughts when enjoying that.) trans. C. Rowe.I like to imagine Theophrastus sitting in the audience and being a bit taken aback… (I don’t know why I think this might bother Theophrastus; he just seems like that kind of person. And I don't think I’d get away with a comment like this in a lecture. Just imagine the questionnaire returns.) It’s a reasonable point, I suppose, if you add some further thoughts. If sex is a natural human activity and sex is very pleasurable and it is impossible to think properly while having sex then perhaps there is a tension between at least some parts of our nature and our wonderful intellectual capacities.
Still, is it just me or does this conjure up all sorts of other images? Perhaps Aristotle had tried it out. (‘Hang on, darling, I’m just wondering about a first figure syllogism…’) And I suppose if you do manage to do a bit of demonstration while having sex, you perhaps are not really engaging properly in either activity. Anyway, it's a shame he doesn't come back to this in 10.5 when he explains how his account of the way in which activities each have a characteristic pleasure explains various phenomena like this.