"The Ptolemaic science on which Hamlet’s protestations are grounded, as Shakespeare knew, was already discredited by the Copernican revolution: the stars aren’t fire, the sun doesn’t revolve around the earth. In such a universe, truth may well turn out to be a liar. Ophelia really does have good grounds to doubt—that is suspect—that Hamlet never loved her. We can see why Hamlet doesn’t want his love letters back—and why he can no longer unburden himself to Ophelia. We are all that is left. Maybe the great secret of the soliloquies is not their inwardness so much as their outwardness, their essaylike capacity to draw us into an intimate relationship with the speaker and see the world through his eyes."
A Year in the Life of William Shakespeare: 1599 by James Shapiro