Article I. On Certain Conscience

39. • DEFINITION. Certain conscience is that by which someone firmly and without fear of erring judges that something is good or evil.

DIVISION. Certitude is usually distinguished as threefold:

1. Metaphysical, which belongs to those propositions in which the attribute belongs essentially to the subject, and therefore is immutable.

2. Physical, which is founded on the constant order by which the world is ruled; this stands firm as long as physical laws are constant, and are considered to have been constant.

3. Moral, which rests upon the laws by which men are ruled in their acts.

Again moral certitude is subdivided into perfect and imperfect. The former is that which is so founded on moral laws that it is clearly perceived that the proposition cannot be false. This is mediately reduced to metaphysical certitude. The latter is that which belongs to those propositions in which it is not absolutely repugnant for error to be present, although it could happen only with the greatest difficulty. This admits various degrees.

Likewise some certitude is direct, which is obtained through certain arguments intrinsic to the matter; another is indirect, which is had from some extrinsic principle, for example, the authority of the Church.

Principles. - I. Certain conscience alone is the right rule of morals. The reason is 1. because everything which is not from faith is sin. Rom. 14. 23; 2. because one acting with a conscience not certain violates the obligation of inquiring into the truth, and therefore sins formally ¹.

¹ Namely, precepts oblige us not only not knowingly to violate them, but also not to transgress them through negligence in inquiring. And from this is the guilt of him who acts while doubting about the honesty of the act. Concerning this matter Suarez (On Censures, disp. 40, sect. 5, no. 12): As long as man does not do what is in him to lay aside doubt, whatever of danger there is in such an operation is imputed to him; for the ignorance which intervenes there is vincible, and therefore cannot excuse from fault. Hence not even he is immune from this fault who, while acting rashly, embraces that part which agrees with the right norm of acting.

II. Morally certain conscience, even imperfect, suffices. The reason is 1. because one acting with such a conscience truly acts from faith; - 2. because absolute certitude often cannot be had; - 3. because it is clear from the common opinion of the Doctors and from universal practice ².

² Whatever is lacking in a plainly firm certitude in the case is always supplied through reflex principles, as will soon be said where probable opinion is treated. For otherwise certitude concerning the honesty of the action must be firm, as below it will occur to note concerning the theories of the probabiliorists.