The concept of wrath contributed to a definition of gender and power. Many medieval authors in 1200 agreed the differences between men and women were based on complexion, shape, and disposition. Complexion involved the balance of the four fundamental qualities of heat, coldness, moistness, and dryness. When various combinations of these qualities are made they define groups of certain people as well as individuals. Hippocrates, Aristotle, and Galen all agreed on that, in terms of biology and sexual differentiation, heat was the most important of the qualities because it determined shape and disposition. Disposition included a balance of the previous four qualities, the four elements and the four humors. For example, the element of fire shared the qualities of heat and dryness: fire dominated in yellow bile or choler, meaning a choleric person was more or hot and dry than others. Hot and dry individuals were active, dominant, and aggressive. The opposite was true with the element of water. Water, is cold and moist, related closely to phlegm: people with more phlegmatic personalities were passive and submissive. While these trait clusters varied from individual to individual most authors in the Middle Ages assumed certain clusters of traits characterized men more than women and vice versa.