Well into the eighteenth century, the only types of mental illness - then collectively known as "delirium" or "mania" - were depression (melancholy), psychoses, and delusions. At the beginning of the nineteenth century, the French psychiatrist Pinel coined the phrase "manie sans delire" (insanity without delusions). He described patients who lacked impulse control, often raged when frustrated, and were prone to outbursts of violence. He noted that such patients were not subject to delusions. He was referring, of course, to psychopaths (subjects with the Antisocial Personality Disorder). Across the ocean, in the United States, Benjamin Rush made similar observations.

In 1835, the British J. C. Pritchard, working as senior Physician at the Bristol Infirmary (hospital), published a seminal work titled "Treatise on Insanity and Other Disorders of the Mind". He, in turn, suggested the neologism "moral insanity".

To quote him, moral insanity consisted of "a morbid perversion of the natural feelings, affections, inclinations, temper, habits, moral dispositions, and natural impulses without any remarkable disorder or defect of the intellect or knowing or reasoning faculties and in particular without any insane delusion or hallucination" (p. 6).

He then proceeded to elucidate the psychopathic (antisocial) personality in great detail:

"(A) propensity to theft is sometimes a feature of moral insanity and sometimes it is its leading if not sole characteristic." (p. 27). "(E)ccentricity of conduct, singular and absurd habits, a propensity to perform the common actions of life in a different way from that usually practised, is a feature of many cases of moral insanity but can hardly be said to contribute sufficient evidence of its existence." (p. 23).

"When however such phenomena are observed in connection with a wayward and intractable temper with a decay of social affections, an aversion to the nearest relatives and friends formerly beloved - in short, with a change in the moral character of the individual, the case becomes tolerably well marked." (p. 23)

But the distinctions between personality, affective, and mood disorders were still murky.

Pritchard muddied it further:

"(A) considerable proportion among the most striking instances of moral insanity are those in which a tendency to gloom or sorrow is the predominant feature ... (A) state of gloom or melancholy depression occasionally gives way ... to the opposite condition of preternatural excitement." (pp. 18-19)

Another half century were to pass before a system of classification emerged that offered differential diagnoses of mental illness without delusions (later known as personality disorders), affective disorders, schizophrenia, and depressive illnesses. Still, the term "moral insanity" was being widely used.

Henry Maudsley applied it in 1885 to a patient whom he described as:

"(Having) no capacity for true moral feeling - all his impulses and desires, to which he yields without check, are egoistic, his conduct appears to be governed by immoral motives, which are cherished and obeyed without any evident desire to resist them." ("Responsibility in Mental Illness", p. 171).

But Maudsley already belonged to a generation of physicians who felt increasingly uncomfortable with the vague and judgmental coinage "moral insanity" and sought to replace it with something a bit more scientific.