The body of Scripture is a doctrine sufficient to live well.
It comprehends many holy sciences, whereof one is principal; others are handmaids or retainers.
The principal science is theology.
Theology is the science of living blessedly forever. Blessed life arises from the knowledge of God: “This is life eternal, that they know thee to be the only very God, and whom thou hast sent, Christ Jesus” (John 17:3). “By his knowledge shall my righteous servant”—viz., Christ—“justify many” (Isa. 53:11). And therefore it arises likewise from the knowledge of ourselves, because we know God by looking into ourselves.
Theology has two parts: the first, of God; the second, of His works.

Perkins, W. (2018). (J. R. Beeke, G. A. Salazar, & D. W. H. Thomas, Eds.). Grand Rapids, MI: Reformation Heritage Books.