The nature of the problems and some previously suggested solutions -- an outline of the problems to be considered -- an outline of some contemporary writers -- a statement of the problems to be solved, and the procedure to be followed -- An examination of the concept of "slef evidence" in thomistic natural law teaching -- An examination of the concept of "self-evidence" in thomistic natural law teaching -- the nature of the problem, some preliminary considerations, and an outline of the procedure to be followed -- S. Thomas's teaching concerning the concept of "self-evidence" in natural law precepts -- The role of the Thomistic concept naturalis inclinatio in our knowledge of self-evident natural law precepts -- a critical assessment of some of the precepts suggested by contemporary writers as being self-evident, together with a summary of the main findings of this chapter -- The Thomistic distinction between primary and secondary natural law precepts, as found in the commentary on the senctences, the summa contra gentiles and the commentary on the nicomachean ethics of aristotle -- recapitulation -- the problem of the character of precepts which are not self-evident -- the problem in the Comentary on the Sentences -- The problem in the Summa Contra Gentiles -- The problem in the commentary on the Ethics -- The Thomistic distinction between primary and secondary natural law precepts, as found in the Summa Theologica -- The doctrine of the division of the division of precepts in question 94, aa. 4-6 -- The doctrine of the division of precepts in question 100, a. 1 -- The doctrine of the division of precepts in question 100 aa. 3 and 11 -- Some comments on the validity and use-fulness of the distinction between primary and secondary precepts -- A statement of the aims of this chapter and an outline of the procedure to be followed -- our assessment of S. Thomas's teaching on the possibility of "logical extension" in natural law -- A final assessment of S. Thimas's teaching on primary and secondary precepts -- The concept of variability among the secondary precepts of natural law -- a discussion on the aims of this chapter and the procedure to be followed -- mere historical changes in positive moral beliefs -- Historical changes correlated with the rational development of man -- Changes in natural law due to the intrinsic complexity of certain particular situations -- the variability of decisions in particular situations due to the contingency of principles -- Variability in natural law due to the "non-obligatory" character of positively formulated precepts -- Variability in natural law due to changes in the intrinsic structure of society