Compared was the effectiveness of two methods of presenting the rules of deduction in studying certain portions of mathematics. The study, involving two sections of a general studies course in mathematics, was conducted during the winter and spring quarters at Southern Illinois University. Section A spent th e entire winter quarter making a formal study of the rules of deduction while section B studied materials which included informal proofs of 74 elementary properties of fields. In the spring quarter, the treatment was reversed. Examinations tested the students' ability to (1) complete information in partial informal proofs, (2) give original informal proofs, and (3) analyze a given proof for correctness or incorrectness. The conclusions formulated from the analysis of data were: (1) there were no significant differences in the students' ability to deal with the above three aspects of informal mathematical proofs according to whether they had or had not previously completed a formal study of the rules of deduction, (2) the students who completed the study of informal mathematical proofs were able to deal with certain aspects of formal proofs better than those students who had not previously completed such a study, and finally (3) the learning of the concepts involved in both these courses is independent of the order in which the courses are presented. (RP)