  Let $E$ be an elliptic curve over $\mathbb{Q}$. Let $\underline{III}(E)$ be a
certain group of equivalence classes of homogeneous spaces of $E$ called its
Tate-Shafarevich group. We show in this paper that this group has finite
cardinality and discuss its role in the Birch and Swinnerton-Dyer Conjecture.
In particular, our result implies the Parity Conjecture, or the Birch and
Swinnerton-Dyer Conjecture modulo 2. It also removes the finiteness condition
of $\underline{III}(E)$ from previous results in the literature of this subject
and makes possible for some computation problems concerning the Strong Birch
and Swinnerton-Dyer Conjecture. In addition, we also give an analogue of the
Hasse-Minkowski Theorem for cubic plane curves.
