The above theory may be thought very odd, but it is partly designed to meet the fourth of our previous questions, namely, “How can we get outside words to the facts which make them true or false?” Obviously we cannot do this within logic, which is imprisoned in the realm of words; we can only do it by considering the relations of words to our other experiences, and these relations, in so far as they are relevant, can hardly be other than causal. I think the above theory, as it stands, is too crude to be quite true. We must also bring in such things as expectedness, which we discussed earlier. But I believe that the definition of truth or falsehood will have to be sought along some such lines as I have indicated. I want in conclusion to indulge in two speculations. The first concerns a possible reconciliation of behaviourism and logic. It is clear that, when we have a problem to solve, we do not always solve it as the rat does, by means of random movements; we often solve it by “thinking”, _i.e._ by a process in which we are not making any overt movements. The same thing was sometimes true of Köhler’s chimpanzees. Now what is involved in the possibility of solving a problem by verbal thinking? We put words together in various ways which are not wholly random, but limited by previous knowledge of the _sort_ of phrase that is likely to contain a solution of our problem. At last we hit upon a phrase which seems to give what we want. We then proceed to an overt action of the kind indicated by the phrase; if it succeeds, our problem is solved. Now this process is only intelligible if there is some connection between the laws of syntax and the laws of physics--using “syntax” in a psychological rather than a grammatical sense. I think this connection is _assumed_ in logic and ordinary philosophy, but it ought to be treated as a problem requiring investigation by behaviourist methods. I lay no stress on this suggestion, except as giving a hint for future investigations. But I cannot think that the behaviourist has gone far towards the solution of his problem until he has succeeded in establishing a connection between syntax and physics. Without this, the efficacy of “thought” cannot be explained on his principles.