If, as Wittgenstein remarks, ‘the meaning of the word “length” is learnt among other things by learning what it is to determine length’ (Philosophical Investigations, p. 225), must we conclude that part of what one knows in knowing the meaning of this word is that length is determined in certain ways, and hence that we should explain the meaning partly by explaining how we determine length, and that the meaning consists partly in certain ways of determining length?

It is not easy to construct a clear argument to that effect, and yet we might naturally so conclude, perhaps on the grounds that generally what we learn in learning X and what we know in knowing X are the same. We learn the names of the professors by learning that that is Professor Jones, that is Professor Smith, etc., and that is also what we know in knowing the names of the professors.