Gian Carlo Rota is always a pleasure to quote, despite he knowing it. One from his reminiscence about Jack Schwartz, in his "Indiscrete Thoughts" Book (TL;DR: M

Gian Carlo Rota is always a pleasure to quote, despite he knowing it. One from his reminiscence about Jack Schwartz, in his "Indiscrete Thoughts" Book (TL;DR: Markov Chains seen as random maps): The first lecture by Jack I listened to was given in the spring of 1954 in a seminar in functional analysis. A brilliant array of lecturers had been expounding throughout the spring term on their pet topics. Jack's lecture dealt with stochastic processes. Probability was still a mysterious subject cultivated by a few scattered mathematicians, and the expression "Markov chain" conveyed more than a hint of mystery. Jack started his lecture with the words, "A Markov chain is a generalization of a function." His perfect motivation of the Markov property put the audience at ease. Graduate students and instructors relaxed and followed his every word to the end. Beuatiful visualizations.