Inconsistent Mathematics

A related but more concise set-theoretic discussion is given here: https://philosophy.stackexchange.com/questions/9741/what-are...

> Escher also actively collaborated with the English mathematician Roger Penrose.

What!!??

... OK. Somehow I always assumed that Escher lived in 1800s. But he lived (1898 – 1972) and he knew Penrose who is older than I thought (born 1931, 87 years old).

I suspected for a moment that the article was intentionally inconsistent, but it checks out.