Fries in his theory of our 'predilection for proofs' emphasizes that the (logical) relations holding between statements are quite different from the relation between statements and sense experiences; positivism on the other hand always tries to abolish the distinction: either all science is made part of my knowing, 'my' sense experience (monism of sense data); or sense experiences are made part of the objective scientific network of arguments in the form of protocol statements (monism of statements).