Input (grade 5): Spencer-Brown was influenced by Wittgenstein and R. D. Laing. LoF also echoes a number of themes from the writings of Charles Sanders Peirce, Bertrand Russell, and Alfred North Whitehead.
Output (grade 7): Spencer-Brown's philosophy was influenced by Ludwig Wittgenstein, R.D. Laing, Charles Sanders Peirce, Bertrand Russell, and Alfred North Whitehead.