A crucial point about notions like unders tanding, thinking effectively, being able to communicate and so on is that they require some subject matter to be understood, thought about and communicated. You cannot just unders tand , think or communicate; there has to be something you are unders tanding, thinking about or communicating. This point has rightly been emphasized by P . H. Hirst (1965), in his criticism of taking a spuriously general mental ability such as the ability to think effectively or to communicate as an aim of education. As Hirst points ou t , depending on the subject matter of one's th inking, quite different abilities and degrees of success might be at s take . A man who can understand and explain Latin poetry sensitively and intelligently might be a complete duffer when it comes to physics; nor is there any necessary t ransfer of ability in one area to ability in another . Moreover, in speaking of a man's under - standing something, we are speaking of an achievement or success he has with some problem or concept, and the criterion of success here is his ability to come up to some public and p r e - viously existing standard of performance. The arguments for this point and its implications are to be found in the account of unders tanding given by Wittgenstein in his 'Philosophical Investigations' (1953).