Because my people hath forgotten me, they have burned incense to vanity, and they have caused them to stumble in their ways from the ancient paths, to walk in paths, in a way not cast up;
Because - rather, And yet; in defiance of the natural order of things.
My people hath forgotten me - (Jeremiah 2:32). This implies a previous knowledge of God, whereas He was unknown to the Gentiles: the Jews' forgetting of God, therefore, arose from determined perversity.
They have caused them to stumble - namely, the false prophets and idolatrous priests have caused the people to stumble.
From the ancient paths - (Jeremiah 6:16): the paths which their pious ancestors trod. Not antiquity indiscriminately, but the example of the fathers who trod the right ways, is here commended.
In a way not cast up - not duly prepared: referring to the center raised of the road. Calvin translates, 'not trodden.' They had no precedent of former saints to induce them to devise for themselves a new worship.