Hermetic Library Fellow T Polyphilus reviews Laws of Form by G Spencer-Brown.

Prior to the vogue of fractal geometry, Laws of Form was conceded by many to be the trippiest math book around. Reading a passage at random out of context might leave one wondering whether the text was political theory, aesthetics, or some other form of philosophy. In his efforts to explicate a Boolean arithmetic underlying the algebra of formal logic, Spencer-Brown works in a conceptually “degenerate” environment where one must attempt to understand the sparest ideas without any systemic framing. The results are positively mystical. 

“[F]or any boundary, to recross is not to cross.” Thelemites will recognize a more rigorous exposition of what Aleister Crowley attempted to express by 0 = 2.