In a book called Laws, Greek philosopher Plato argued that drinking with someone at a symposium (drinking party) was the simplest, fastest and most reliable way of testing someone's character. This is because wine stimulates the emotions – including desires for pleasures of questionable moral worth. Becoming aware of one's emotions and desires and learning how to maintain balance and a virtuous life are essential skills, according to Plato.
Source: Koeplin, A. L. (2006). Drinking, Fighting, and Singing. Loyola Marymount Univ. Colloquium Series.