Justified True Belief?

flesh and blood has not revealed this to you, but My Father who is in heaven. (Matt.16:17)
People usually do have reasons for their beliefs, though not all may be able to instantly enumerate all their reasons when asked for. The believer in Chi power might even demonstrate his grounds of belief. So will the homeopath, the allopath, the evolutionist, the Yogi, the Advaitin, and the astrologer. But, it is also possible that one cannot demonstrate proofs and yet decide to go on with what one is convinced about, in whatever sense whatever. The Jews knew that there were no witnesses to incriminate the Christ; however, when He announced who He was, they decided that His statement was proof enough of blasphemy. But, on what grounds?

The work of a preacher is certainly to persuade by means of reasoning. For some it may mean persuasion through exposition of scriptures; to others, through spiritual encounter and signs and wonders; to others, through contextually relevant reasoning (as in the case of Paul in Athens). However, no preaching, no matter how profoundly apologetical and persuasive it is, can ever convince any man no matter how wise and persuasive words may seem.
And I, brethren, when I came to you, did not come with excellence of speech or of wisdom declaring to you the testimony of God. For I determined not to know anything among you except Jesus Christ and Him crucified. (1Cor.2:1-2)
For our boasting is this: the testimony of our conscience that we conducted ourselves in the world in simplicity and godly sincerity, not with fleshly wisdom but by the grace of God, and more abundantly toward you. (2Cor.1:12)
Now, this doesn’t mean that a man’s will is not involved. The very idea of responsibility and accountability involves the irrefutable fact that a man is responsible for his beliefs and his actions. Sloth and indulgence make an inexcusable fool by his own choice. And, yet, the slothful are not without reasons.
The lazy man will not plow because of winter; he will beg during harvest and have nothing. (Prov.20:4)
Certainly, flesh and blood cannot reveal Christ to man. Yet, divine revelation must be met by faith; or else, it is ineffective.
the word which they heard did not profit them, not being mixed with faith in those who heard it. (Heb.4:2)
It is possible for one to be arduous, diligent, and passionate in the path that he considers to be true. In other words, one may be misled and yet not because of sloth. However, it is certain that if there is true sincerity in a quest, then obedience to faith will not be a problem when revelation comes.
And I advanced in Judaism beyond many of my contemporaries in my own nation, being more exceedingly zealous for the traditions of my fathers. But when it pleased God, who separated me from my mother's womb and called me through His grace, to reveal His Son in me, that I might preach Him among the Gentiles, I did not immediately confer with flesh and blood (Gal.1:14-16)

although I was formerly a blasphemer, a persecutor, and an insolent man; but I obtained mercy because I did it ignorantly in unbelief. (1Tim.1:13)

I was not disobedient to the heavenly vision (Acts 26:19)

But the hour is coming, and now is, when the true worshipers will worship the Father in spirit and truth; for the Father is seeking such to worship Him. (Jn.4:23)