Physicists do it at the right moments. Physicists do it with force. Physicists do it on the spur of the moment. Probabilists Probabilists do it on random walks. Probabilists do it stochastically.
Pure mathematicians do it rigorously.
Quantum physicists Quantum physicists can either know how fast they do it, or where they do it, but not both. Quantum physicists can either know when they do it, or with how much energy they do it, but not both. Real analysts Real analysts do it almost everywhere Real analysts do it uniformly. Ring theorists do it non-commutatively. Ring theorists do it ideally.