This document discusses biological weapons and why they have not been used more widely, despite their lower cost compared to nuclear weapons. It presents three key reasons why biological weapons have not seen more widespread use: 1) They are harder to develop than initially thought due to technical challenges; 2) People have an aversion to disease and do not want to inflict suffering through biological agents; 3) Nuclear weapons were developed first and established a norm against their use, which also applies to biological weapons. The document questions what should be done about ongoing biotechnology advances that could lower the technical barriers to developing biological weapons.