The idea then that experience will _at any rate_ confer knowledge is a false idea. It is not true, that the old physician, _as a matter of course_, knows more than he did when he was young. If he has observed well, he does know more; but if he has not observed well, he not only does not know more, but he knows less. In the latter case, he may indeed have more ideas and opinions than he had when he began his practice, but he does not know as many real ascertained facts, and those which he does know are so encumbered with the long accumulating rubbish of error, that they are of little use to him. It is easier to adopt a theory with a corresponding system of remedial means, or even to originate one, than it is to encounter the labor of strict daily observation at the bedside of the sick. Many physicians pursue the former course, and go through with a routine of practice from year to year. If they have some tact in managing the capricious credulity of the public, they succeed in attaining the object at which they aim. These followers of a _system_ are generally considered by the community as very rational and scientific men. Some of them, though they live on the opinions advanced, and the facts discovered by others, contrive to get up quite a reputation for originality, by making so much account of these opinions and facts, that the public awards to them, in part at least, the credit of their discovery. It gives them a sort of eclat to stand out from their medical brethren, as the advocates of some peculiarity of doctrine or practice. The medical profession has had too much to do with theories, and modes, and systems. Every prominent theory can be shown to be unsubstantiated by facts, and is therefore valueless. Every mode, or system of practice, however numerous are the facts which are adduced for its support, can be shown to exclude many facts of a valuable character; and being thus exclusive, it must lead to practical error. _All these systems therefore should be discarded._ A true eclecticism should be introduced into medicine, and it should have relation not to opinions and theories, but to facts only. Whenever a fact is really ascertained, it should be treasured up in the storehouse, ready for practical use. If it be apparently inconsistent with other facts, this is no reason for rejecting it. If it be really proved, it should be received, and its consistency with other facts may afterward be discovered. Indeed, quite a large proportion of the facts practically applied in medicine, are _independent_ facts, neither explained themselves, nor capable as yet of being used in the explanation of other facts. I have alluded to this point before. A single example here will suffice. No fact in medicine is better established than that arsenic in almost all cases cures hemicrania, or periodical neuralgia on one side of the head. How or why it does this no one knows. The bare fact is known.