Tertullian, Against Marcion 17

They burst out of their corner and say: "One single work is enough for our God: He freed humanity by His supreme, paramount goodness — a work to be preferred to all places." (The manuscript actually reads 'locusts', but the absurdity is theirs.) Oh, a greater God! — whose work is so great it cannot be found anywhere except in the man of the lesser God! But the order of proof is backwards. First you have to prove He is God through the standard — His works — then, and only then, through His benefits. First you ask whether He exists, and then what kind of God He is. Existence is settled by works; character by benefits. You don't establish His existence simply because He is said to have freed humanity; you establish His existence first, and then you can say He freed humanity — so that it also becomes established whether He actually did free anyone, since He was capable both of existing and of not freeing. How, then, can He be believed to exist just because He is said to have freed, when He was capable both of existing and of not freeing?

Now, in this very article — drawn away from the question of the unknown God — if it is sufficiently established that He neither created anything nor ought to have created, so that He might be known through His works (because if He had existed, He ought to have been known, and certainly from the beginning of things — for it was not fitting for God to have stayed hidden) — we must go back to the origin of the question of the unknown God so that I can shake off its other branches as well. First it will be necessary to ask: He who presented Himself to knowledge only later, why later and not from the beginning of things, for which He was certainly necessary, since He is God, and indeed all the more necessary, because the better He is, the less He ought to have been hidden? It cannot be said that there was neither material nor cause for knowing God, since both humanity was in the world from the beginning — the very humanity He now assists — and the malice of the Creator, against which, as good, He assists. Therefore, either He ignored both the cause and the material of His necessary revelation, or He doubted, or He was unable, or He was unwilling. All of these are unworthy of God, especially the best God. But we will fill out this point elsewhere with the reproach of His late revelation, just as now we settle it with sheer demonstration.