I did not write to you because ye have not known the truth, but because ye have known it, and because no lie is of the truth.

I have written to you, not because you are ignorant of the truth, but because you know it, and you know that nothing false comes from the truth.

I have not sent you this letter because you have no knowledge of what is true, but because you have knowledge, and because that which is false has nothing in common with that which is true.

I have not written to you as to ones who are ignorant of the truth, but as to ones who know the truth. For no lie is of the truth.

I am not writing to you because you do not know the truth, but because you do know it, and because no lie can come from the truth.

And that no lie is of the truth. He concedes to them a judgment, by which they could distinguish truth from falsehood; for it is not the dialectic proposition, that falsehood differs from truth, (such as are taught as general rules in the schools;) but what is said is applied to that which is practical and useful; as though he had said, that they did not only hold what was true, but were also so fortified against the impostures and fallacies of the ungodly, that they wisely took heed to themselves. Besides, he speaks not of this or of that kind of falsehood; but he says, that whatever deception Satan might contrive, or in whatever way he might attack them, they would be able readily to distinguish between light and darkness, because they had the Spirit as their guide.

I have not written unto you because ye know not the truth - You are not to regard my writing to you in this earnest manner as any evidence that I do not suppose you to be acquainted with religion and its duties. Some, perhaps, might have been disposed to put this construction on what he had said, but he assures them that that was not the reason why he had thus addressed them. The very fact that they did understand the subject of religion, he says, was rather the reason why he wrote to them.
But because ye know it - This was the ground of his hope that his appeal would be effectual. If they had never known what religion was, if they were ignorant of its nature and its claims, he would have had much less hope of being able to guard them against error, and of securing their steady walk in the path of piety. We may always make a strong and confident appeal to those who really understand what the nature of religion is, and what are the evidences of its truth.
And that no lie is of the truth - No form of error, however plausible it may appear, however ingeniously it may be defended and however much it may seem to be favorable to human virtue and happiness, can be founded in truth. What the apostle says here has somewhat the aspect of a truism, but it contains a real truth of vital importance, and one which should have great influence in determining our minds in regard to any proposed opinion or doctrine. Error often appears plausible. It seems to be adapted to relieve the mind of many difficulties which perplex and embarrass it on the subject of religion. It seems to be adapted to promote religion. It seems to make those who embrace it happy, and for a time they apparently enjoy religion. But John says that however plausible all this may be, however much it may seem to prove that the doctrines thus embraced are of God, it is a great and vital maxim that no error can have its foundation in truth, and, of course, that it must be worthless. The grand question is, "what is truth;" and when that is determined, we can easily settle the inquiries which come up about the various doctrines that are abroad in the world. Mere plausible appearances, or temporary good results that may grow out of a doctrine, do not prove that it is based on truth; for whatever those results may be, it is impossible that any error, however plausible, should have its origin in the truth.

I have not written, etc. - It is not because ye are ignorant of these things that I write to you, but because you know them, and can by these judge of the doctrines of those false teachers, and clearly perceive that they are liars; for they contradict the truth which ye have already received, and consequently their doctrine is a lie, and no lie can be of the truth, i.e. consistent with Christianity.

(22) I have not written unto you because ye know not the truth, but because ye know it, and that no lie is of the truth.
(22) The taking away of an objection, He did not write these things to men who are ignorant of religion, but rather to those who know the truth well, yes so far that they are able to discern truth from falsehood.

I have not written unto you,.... Either this epistle, or rather what particularly here regards those apostates from the truth, in order to shun them and not be deceived by them: the apostle here obviates an objection that he saw might be made upon what he last said, that they knew all things; and, if so, why then did he write the things he did, since they knew them before? to which he answers, that he did not write to them as to ignorant, but as to knowing persons:
because ye know not the truth, but because ye know it: the Father, who is the God of truth; Christ, who is truth itself; and the Spirit, who is the Spirit of truth; and the Gospel, which is the word of truth; and the Scriptures, which are the Scriptures of truth, and from whence truth is to be fetched, and by them to be confirmed and defended; and which, if they had not known, it would have been to no purpose for him to have written to them about the antichrists that were come into the world; and though they did know the truth, it was very proper to put them in remembrance of it, and to establish them in it, against these deceivers, which supposes former knowledge of it:
and that no lie is of the truth; either springs from it, or is according to it, but just the reverse. The apostle has respect to the errors and heresies of the above apostates, which were flagrant contradictions to the Gospel, and as distant from it as a lie is to truth; and of such lies, and of those liars, he speaks in the next verses. The Arabic version reads, "and that every liar is not of the truth".

but because ye know it, and that, &c.--Ye not only know what is the truth (concerning the Son and the Father, 1-John 2:13), but also are able to detect a lie as a thing opposed to the truth. For right (a straight line) is the index of itself and of what is crooked [ESTIUS]. The Greek is susceptible of ALFORD'S translation, "Because ye know it, and because no lie is of the truth" (literally, "every lie is excluded from being of the truth"). I therefore wrote (in this Epistle) to point out what the lie is, and who the liars are.

I have written - Namely, 1-John 2:13. To you because ye know the truth - That is, to confirm you in the knowledge ye have already. Ye know that no lie is of the truth - That all the doctrines of these antichrists are irreconcilable to it.