PERSON@1 -LRB- NUMBER@1 April NUMBER@2 -- NUMBER@3 April NUMBER@4 -RRB- was an MISC@1 philosopher who worked primarily in logic , the philosophy of mathematics , the philosophy of mind , and the philosophy of language .

April NUMBER@3 , NUMBER@4 -RRB- was an MISC@2 philosopher . He worked mainly in the basics of logic , the philosophy of mathematics , the philosophy of mind , and the philosophy of language .
