He broke with the positivist orientation of the science and philosophy of his time , believing that experience is the source of all knowledge . He broke with the positivist orientation of the science and philosophy of his day , yet he elaborated critiques of historicism and of psychologism in logic . Not limited to empiricism , but believing that experience is the source of all knowledge , he worked on a method of phenomenological reduction by which a subject may come to know directly an essence .