Post: In Devarim 13, in parashat Reeh, we read:
This seems rather theologically strange, that Hashem would do this. But I see how this can be justified -- that this is a test to see if you are truly committed. Knowing it is a test, because of this pasuk, might spoil some aspect of the test. After all, if you know that this is really Hashem empowering the prophet, then the false prophet bringing signs or wonders is not such great proof of his own deity's existence or power. Though the test might now be whether to believe the Torah or the prophet.
At any rate, despite this being the simple implication of the pasuk, Ibn Caspi rejects this. He writes:
Of course it isn't Hashem that is doing this to trick you! Rather, the false prophet accomplishes this using whatever mechanisms he uses to generate the miracle or the sign. Hashem isn't causing this.
However, the ignorant masses -- you know, the type who are persuaded by Rav Amnon Yitzchak -- will believe this sign, and will not be able to see to the heart of the matter. Therefore, the Torah delivers a sort of falsehood that the hamon am will be able to understand. Treat it as a decree of the king not to listen to this "miracle" worker. And because of their feeble intellect, He gives them a good reason which is fitting for them, that Hashem is "testing them". And this false reason is not strictly false, for after all, Hashem is the First Cause.
This fits in well with Ibn Caspi's general application of his particular extension of the idea of dibra Torah kilshon benei Adam. Though Ibn Caspi does not use that technical term here.