This is a very rough division of different senses of implicit faith. It’s NOT definitive. But, each grouping has important and significant differences that need to be heeded. Even where nuance might be needed or even correction, this is all meant to be based upon Thomistic foundations.
A. Meaning related to Dogmatic Development—Implicitation as unfolding of the truths of the faith over time
B. Meaning regarding implicitation among various persons right now
B1. The way that some Catholics today have implicit faithful in some mysteries (one would speak of maiores and minores)
B2. The way that some Orthodox today have implicit faith in some mysteries
B3. The way that some Protestants today have implicit faith in some mysteries
C. The way that those who were directly involved in salvation history had truths of faith — Development of Revelation
- Mosaic Revelation
- Revelation during the age of the "law of nature" (as they used to say)
D. Implicit faith in the distant cases of those who are saved by a kind of surd in voto baptismi. This is necessary for the case found even in Pius IX. (Although, when he speaks of those who follow the natural law, though they know not the gospel, he does somewhat naturalize this process. It makes it sound as though God will give supernatural recompense after a life of natural rectitude. But in fact, it is a question of implicit, supernatural faith, founded upon a very weak noetic foundation.)
Such implicit faith is also acknowledged by Scholastics prior to this, and also by Hugon, Garrigou, and even, to a degree, Fenton; I think it is given excellent analysis by Maritain, Journet, Labourdette, and Jean-Hervé Nicolas. (I am thinking here of the case analyzed in the article on the Immanent dialectic of the first free act, by Maritain. As Nicolas points out, this is different from a pre-volitional, natively positive inclination that would be a kind of anonymous Christianity on the model of K. Rahner.)