It is sometimes held that Logic is rather an art than a science, or at any rate that it is an art as well. In considering this question, we must remember that there are two senses of the word art. We may say that a man understands the art of navigation when he is skilful in handling a ship, though he may be unable to explain the principles which he follows; or we may say that he understands it, when he is familiar with the principles of navigation, as a piece of book-work, though he may never have