One of the traditional ideas about personality was Temperament Theory which probably originated from Egypt and was developed by Hippocrates into a medical theory. In the tenth century, it was extended by Avicenna and had been used for many years in medicine. Do you know when this idea was widely replaced by modern methodology in medicine (especially in the West)? Is it still a useful theory in psychology?
Although the original humorism put forth by Hippocrates and Galen based on Egyptian and Mesopotamian influences was rejected by science as a general theory explaining all diseases and disabilities, a later version restricted to temperaments in psychology, that removed their link to supposed "bodily fluids", survives until today. The psychological shift can be traced to Avicenna (980–1037), who used temperaments to describe "emotional aspects, mental capacity, moral attitudes, self-awareness, movements and dreams", and Culpeper (1616–1654), who discarded the theory that temperaments were influenced by fluids. Modern psychology of temperaments was strongly influenced by Kant (1724-1804). As far as the theory that all ills come from excess or deficit in one of the four humors, its rejection was gradual.
The starting point seems to be the Black Plague of 14th and 15th centuries. Anatomical work of Vesalius (1514-1564) undermined many of Galen's traditional assertions, including those about blood and other fluids. However, the transfer to the modern theory of infectious diseases spread by microorganisms took a long time. Even though "little animals" were discovered by Leeuwenhoek in 1677 it seems that only Jenner (1749-1823) definitively linked them to the spread of a disease in 1796. He inoculated patients with a cow-pox virus to prevent them from developing small pox, the term he used for his treatment, "vaccination", is still in use today. What complicated things was the widely believed spontaneous generation theory that microorganisms could appear spontaneously under favorable circumstances, which was only fully disproved by Pasteur in 1862 leading to acceptance of sterilization and immunization, anticipated by Jenner.
On the psychological side Culpeper observed that temperaments may not be pure, and some people have an admixture of two. This was a precursor of the modern view that temperaments appear in a spectrum rather than as separate poles. After him the theory seemed to fade away for a while, and according to a 19-th century historian Dircksen it was Kant who revived it. In 1760-s he suggested a non-traditional interpretation of "phlegma as strength" and "substitute for wisdom". Later this led to a theory of five temperaments, where an additional "neutral" temperament was added to the traditional four, although Kant himself favored the foursome. He also described melancholy as capable of "genuine virtue". In the 20-th century on the other hand, some authors characterized melancholy as an affliction to be treated rather than a healthy temperament.
But those were tweaks, after Kant the theory was accepted in one form or another by many 19-th century psychologists. In the 20-th century not only Freudians (Adler, Jung), but even physiologists like Pavlov accepted it as well. Pavlov observed temperaments in his experiments with dogs:
"One of the things Pavlov tried with his dogs was conflicting conditioning -- ringing a bell that signaled food at the same time as another bell that signaled the end of the meal. Some dogs took it well, and maintained their cheerfulness. Some got angry and barked like crazy. Some just laid down and fell asleep. And some whimpered and whined and seemed to have a nervous breakdown."
His idea was that temperaments can be recovered from simple binary classification of brain's capabilities for excitation and inhibition. Perhaps the most extensive modern theory of temperaments is due to Eysenck, a behaviorist who developed Pavlov's idea into a detailed theory, and used statistical factor analysis to support genetic origins of temperaments.