Gaudium et Spes 16 is a single paragraph:
In the depths of … conscience, (humankind) detects a law which it does not impose upon itself, but which holds it to obedience. Always summoning (a person) to love good and avoid evil, the voice of conscience when necessary speaks to (the) heart: do this, shun that.
Is the urging of conscience so straightforward? I think so. Long deliberations may be more the result of the attempt to squirm away.
For (humankind) has in (its) heart a law written by God; to obey it is the very dignity of (humankind); according to it it will be judged.(Cf. Rom. 2:15-16) Conscience is the most secret core and sanctuary of a (person). There (the person) is alone with God, Whose voice echoes in (the) depths.(Cf. Pius XII, radio address on the correct formation of a Christian conscience in the young, March 23, 1952: AAS (1952), p. 271) In a wonderful manner conscience reveals that law which is fulfilled by love of God and neighbor.(Cf. Matt. 22:37-40; Gal. 5:14)
GS 16 reminds us that conscience is a point of congruence between Christians and non-Christians:
In fidelity to conscience, Christians are joined with the rest of (people) in the search for truth, and for the genuine solution to the numerous problems which arise in the life of individuals from social relationships.
And the conscience must be exercised, lest it lose its vigor:
Hence the more right conscience holds sway, the more persons and groups turn aside from blind choice and strive to be guided by the objective norms of morality. Conscience frequently errs from invincible ignorance without losing its dignity. The same cannot be said for a (person) who cares but little for truth and goodness, or for a conscience which by degrees grows practically sightless as a result of habitual sin.
A direct and brief assessment of conscience, leading the way for upcoming discussion on goodness, life and death, and making moral choices for the betterment of the planet.