This document discusses how browser fingerprinting can be used as a factor in multi-factor authentication. It explains that authentication is based on probability, not a binary yes/no. Using multiple authentication factors like something you know (password), something you have (browser), and something you are (biometrics) multiplies the probabilities of each being incorrect, making the overall authentication more secure. The document proposes that a user's unique browser configuration determined via fingerprinting could serve as an additional authentication factor, improving security without additional hardware costs. Objections about fingerprint or browser changes are addressed.