Fr. Louis Guardiola, C.P.M.
Conformity of mind with reality. Three kinds of conformity gives rise to three kinds of truth. In logical truth, the mind is in conformity or in agreement with things outside the mind, either in assenting to what is or denying what is not. In metaphysical or ontological truth, things conform with the mind. This is primary conformity, when something corresponds to the idea of its maker, and it is secondary conformity when something is intelligible and therefore true to anyone who knows it. In moral truth, what is said conforms with what is on one’s mind. Tis is truthfulness and it’s opposite is falsehood.
The untrue in word, thought or appearance. What is untrue in thought is logically false. The untrue in written or spoken word is a lie. And the misleading or deceptive in appearance is ontologically false, or false in being, and is the occasion of error in being. Deceit is a deliberate effort to conceal the truth, whether in speech, writing, or action. The motives can be from a number of things such as avarice, a desire for base gain or pride, etc.