Kant- The first and second antinomies

The first two antinomies, the first having to do with space and time, and the second having to do with the simple and composite, both have opposing propositions (the thesis and antithesis). Whereas in the 3rd and 4th antinomies Kant argues that both the thesis and the antithesis are both actually true (and only mistaken to be contradictory when one takes phenomena to be noumena), Kant argues that the thesis and antithesis of the 1st and 2nd are both false. One might wonder how to contradicting propositions can both be untrue. It seems to be like the law of non contradiction in logic: P v ~P (P or not P), i.e., either something is the case or it is not. Kant explains that it is possible for two ocntradicting statements to both be false when "the concept lying at the ground of both of them is self-contradictory". Kant gives the example of a square circle. Two contradictory statements about square circles can both be false because the concept of a square circle is inherently contradictory. Because of that, any proposition which asserts anything about square circles is false. In the same way, when it comes to the question of whether or not space and time are infinite, or whether the constituents of the world are simply or composite, making any assertion of either the thesis or antithesis of either antinomy is assuming that experience is fit to give an answer. Becausethe world given to us IS equivalent to our experience, to suppose that our experience has the property of being simple or composite or infinite or finite is a mistaken notion.