 Practical reason, in Aquinas’ view, has both one absolutely first principle and many truly first principles: ST I-II q. 94 a. 2. The absolutely first principle is formal and in a sense contentless. Like the logical principle of non-contradiction which controls all rational thought, it expresses, one might say, the pressure of reason and is so far from being empty of significance and force that its form may be regarded as the frame, and its normativity the source, for all the normativity of the substantive first principles and of the moral principles which are inferable from them. Aquinas articulates it as “Good is to be done and pursued, and bad avoided” (ibid.).