Theophilus. Everything, Academicus, is, and must be, its own proof; and can only be known from and by itself. There is no knowledge of anything, but where the thing itself is, and is found, and possessed. Life, and every kind and degree of life, is only known by life; and so far as life reaches, so far is there knowledge, and no farther. Whatever knowledge you can get by the searching and working of your own active reason, is only like that knowledge, which you may be said to have got, when you have searched for a needle in a load of straw, till you have found it.