In January 1935, Oppenheimer visited Princeton University as a visiting faculty member on an invitation. After staying there and interacting with Einstein, Oppenheimer wrote to his brother Frank Oppenheimer in a letter thus, "Princeton is a madhouse: its solipsistic luminaries shining in separate & helpless desolation. Einstein is completely cuckoo.... I could be of absolutely no use at such a place, but it took a lot of conversation & arm waving to get Weyl to take a no”. Oppenheimer's initial harsh assessment was attributed to the fact that he found Einstein highly skeptical about the quantum field theory. Einstein never accepted the quantum theory; in 1945 he said: "The quantum theory is without a doubt a useful theory, but it does not reach to the bottom of things. I never believed that it constitutes the true conception of nature". Oppenheimer also noted that Einstein became very much a loner in his working style.