The other mode of believing, that is to say, by implicit faith, is based on various principles. First, by reason of an explicit belief of one revealed truth others are said to be believed implicitly on account of the formal object of faith, namely, the veracity of God who reveals; whereby all the truths of revelation are so connected together that it is impossible for any one to believe one article because God has revealed it, without being at once prepared to believe all other articles of His revelation when they are sufficiently proposed. And this is to believe implicitly. Whereas to deny one article of faith is implicitly to deny all because we cannot give the adhesion of faith to the rest should we withhold it from one. Just as whoever detests one sin for God's sake, must virtually and implicitly detest all.
Secondly a man may believe with implicit faith from his relation to others who believe explicitly. It is in this way the simple faithful are said to believe all things that the Church believes, or the Apostles taught, though they do not know actually what all these things are.
Thirdly, there may be this implicit faith by reason of some truth that is believed explicitly, and that in many ways. For example, because one proposition is contained in some other, as a conclusion is in a principle from which it may be evidently drawn. Thus, he who believes that Christ is man, believes implicitly that He is visible. Or, because one proposition is connected with another in reality, or by actual identity, even though such connection cannot be known without faith. Thus he who believes that God is infinite, believes implicitly that He is Three in Persons. Or again, the particular is known in the universal, as is self-evident. And lastly, the circumstances of a revealed mystery are said to be known implicitly in its substance. Thus he who believes that Christ is the Redeemer of the world, believes implicitly that He died for the salvation of men. And such like.*