Christian Thomasius, a German Enlightenment philosopher and jurist published one of the earliest accounts of systematic personality assessment. Originally presented in the form of a letter under the wonderful title 'New Discovery of a Solid Science, Most Necessary for the Community, for Discerning the Secrets of the Heart of Other Men from Daily Conversation, Even Against Their Will;' Thomasius suggested that the key to assessment lies in the ability to differentiate between a person's natural and affected feelings along with the knowledge that people resist overt displays of crude emotion.

Building on his work in a later publication, Thomasius produced the first quantitative psychological rating scale based on four inclinations: 1. Rational love (Vernünftige Liebe), 2. Sensuousness (Wollust), 3. Ambition (Ehrgeiz), 4. Acquisitiveness (Geldgeiz). Thomasius believed that we all possess these inclinations to a greater or lesser extent and that one of the four will always be dominant. In order to measure individual differences Thomasius allocated 60 points to the strongest inclination, a minimum of 5 points to the weakest inclination and scored the two remaining inclinations by calculating the difference between the highest and lowest scores.

See following link for free personality psychology information and resources.

Personality Psychology