The Birthday of Paul Halmos (1916) – Author of ‘I Want to Be a Mathematician’

Paul Halmos was a mathematician and writer known for his clear exposition. He wrote ‘Finite‑Dimensional Vector Spaces’, ‘Naive Set Theory’, and the autobiography ‘I Want to Be a Mathematician’. He introduced the ‘iff’ (if and only if) notation and the tombstone symbol ∎ for the end of a proof. He believed that mathematics is best understood by reading and writing proofs. He also studied Hilbert space operators (Halmos’s problem on the invariant subspace). His advice: ‘Don’t just read mathematics; do mathematics.’