4. The changes of hair described, with hardly an exception, cannot be conceived as resulting from the factors of organic evolution--heredity, variation, adaptation and selection--indeed no serious attempt has been made to connect them in any way with utility. [60] Jevons, _Principles of Science_, p. 269. [61] E. Ray Lankester. _Advancement of Science_, p. 7. Causation. For my sins, the most obvious of which is that I made an unfortunate choice of my first birthday, I had to learn up the dreary pages of Mill’s _Logic_ and those of other philosophers, for the pleasure of taking a medical degree, and was reduced to that orthodox state of mind in which one was forbidden to suppose that, in the world around where common men and women, every day and all day, are tracing causes for the occurrences they see on every hand, there was anything at work which could be truly called a cause. It was but natural to fall into the nihilism of the Mill and Karl Pearson school. Having neither the knowledge nor the hardihood to discern that their bewildering notions of causation could be gainsaid, I had to remain submissive and as much contented as possible with their views of an elusive subject. This state of passive resistance was not relieved until I had the great advantage of reading a valuable book by the late Dr. Mercier on Causation, which seems to have let some fresh air into the musty doctrines of the orthodox and autocratic philosophers. No one who has read this work can doubt that after all there is such a process as causation, and that to find a cause for events is not merely a pursuit of the vulgar, but a duty of scientific persons. Mill appears to have given eighteen different accounts of causation and to have contradicted himself over and over again in his works dealing with this puzzle, devised mainly by Hume and himself; and his successors, such as Dr. Mc’Taggart, the Hon. Bertrand Russell of “Dog Fight” fame, Mr. Welton and Prof. Karl Pearson, have only got as far as to reduce the number of his definitions and put his views into more modern, but equally misleading terms. Without any disparagement of their other claims to respect and admiration, one may venture to throw overboard this school of philosophers when considering causation, and one may walk and talk in a clearer atmosphere. The subjects here considered are cause, effect, result, reason, evidence and proof, and all can be seen to enter into my small thesis. They may then be defined, according to Dr. Mercier, as follows:-- 1. A cause is an action, or cessation of action, connected with a sequent change or accompanying unchange, in the thing acted on, or more shortly for my purpose _a cause is an action upon a thing_. 2. An effect is a change connected with a preceding action. 3. In reference to causation a reason means the cause of an unchange. 4. A result is the changed state that is left when an effect has been produced.