It is common to suppose that people are characterized by their rationality, and the most evident display of our rationality is our capacity to think. This is the rehearsal in the mind of what to say, or what to do. Not all thinking is verbal, since chess players, composers, and painters all think, and there is no a priori reason that their deliberations should take any more verbal a form than their actions. It is permanently tempting to conceive of this activity in terms of the presence in the mind of elements of some language, or other medium that represent aspects of the world (see language of thought hypothesis, ideas). But the model has been attacked, notably by Wittgenstein, as insufficient, since no such presence could carry a guarantee that the right use would be made of it. And such an inner presence seems unnecessary, since an intelligent outcome might arise in principle without it. See also animal thought.