You can also use nonstandard analysis to derive Black-Scholes, replacing stochastic calculus by a random walk with infinitesimal steps. https://ieeexplore.ieee.

You can also use nonstandard analysis to derive Black-Scholes, replacing stochastic calculus by a random walk with infinitesimal steps. https://ieeexplore.ieee.org/document/261595 https://ieeexplore.ieee.org/document/261595 (don't see an ungated version)