Mankind have always within the period of written records (a mere trifle in the lapse of time since man became man) regarded mental defect and aberration as due to fantastic causes. To this day we use the word “lunatic” for one of the two typical forms of mental aberration: we imply that the moon is concerned in its production. The other form of brain-failure has appropriated the term “idiot,” which, it is surprising to find, was less than two centuries ago applied in common speech to any person who was characterised by independence of judgment. The term “softy” is a common and really more suitable term for this class, whilst “cracked” is the word applied to a lunatic. The notion that mental aberration is due to “possession” by evil spirits, which can be expelled and the patient accordingly cured, was prevalent a century ago, and the belief is common at the present day (though quite erroneous) that people “go mad” in virtue of some immaterial and unaccountable influence, and may therefore “go sane” again. The lunacy laws and the laws relating to the care of the feeble-minded in this country are admitted to be tainted with ignorance and misconception, and both are in process of correction by the Government of the day. The approved professional terms used in distinguishing the varieties of “the mind diseased” are not accepted with much favour by the public, and it is unnecessary to introduce them here. The important fact is that persons of diseased mind may be separated into two groups—(_a_) the idiots or softies, and (_b_) the lunatics or cracked people. The idiotic group are those with a defective amount or quality of brain substance (whether the skull itself is small or abnormally distended by “water on the brain”), and are more or less incapable of being educated. They are often subject to epileptic fits, and are usually weakly in build, though they sometimes have great muscular strength. The “feeble-minded,” of whom so much has lately been written, owing to the recent report of a Government Commission, belong to this group. They are distinguished from the more marked section of idiots in that they are not absolutely devoid of some intelligence, and are capable, under proper supervision, of some degree of self-control. Some of them even can take part in industrial operations, though they require constant direction when so employed, and are never, even in the least serious cases, susceptible of mental development beyond a strangely and abruptly limited degree. Contrasted with the idiots are the lunatics; they often are gifted with the highest receptivity, and frequently are men or women of the highest education and intellect, normal in every feature of body and mind except that their mental machinery works in a defective, “mad” way as to one or more subjects—often only as to one subject or class of subjects. They exhibit in different individuals a vast variety of illusions and