of procedure he has never tried to give an account to himself.

That he has a mind he cannot doubt, and he has some idea of the
difference between it and certain other minds; but even the most ardent
champion of the plain man must admit that he has the most hazy of
notions touching the nature of his mind. He seems to be more doubtful
concerning the nature of the mind and its knowledge than he is
concerning the nature of external things. Certainly he appears to be
more willing to admit his ignorance in this realm.

And yet the man can hold his own in the world of real things. He can
distinguish between this thing and that, this place and that, this time
and that. He can think out a plan and carry it into execution; he can
guess at the contents of other minds and allow this knowledge to find
its place in his plan.

All of which proves that our knowledge is not necessarily useless
because it is rather dim and vague. It is one thing to use a mental
state; it is another to have a clear comprehension of just what it is
and of what elements it may be made up. The plain man does much of his
thinking as we all tie our shoes and button our buttons. It would be
difficult for us to describe these operations, but we may perform them
very easily nevertheless. When we say that we _know_ how to tie our
shoes, we only mean that we can tie them.

Now, enough has been said in the preceding sections to make clear that
the vagueness which characterizes many notions which constantly recur
in common thought is not wholly dispelled by the study of the several
sciences. The man of science, like the plain man, may be able to use
very well for certain purposes concepts which he is not able to analyze