This thinker modified Frege's idea of unsaturated concepts in creating propositional functions in an essay that examines the 
This thinker modified Frege's idea of unsaturated concepts in creating propositional functions in an essay that examines the sentence "the present King of France is not bald." He discussed a hypothetical claim about a teapot orbiting in space between the Earth and Mars and wrote "On Denoting". This man argued against the historical existence of Jesus in his essay "Why I Am Not a Christian". For 10 points, name this author, who used symbolic logic to examine arithmetic in co-authoring the Principia Mathematica with Alfred North Whitehead.
This thinker modified Frege's idea of unsaturated concepts in creating propositional functions in an essay that examines the sentence "the present King of France is not bald."
Bertrand Russell