[I]t was thought many years ago that no one could understand the heart. The heart was called the .

The heart hath its mystery, and who may reveal it,
Or who ever read in the depths of their own? —
How much, we never may speak of, yet feel it,
But, even in feeling it, know it unknown!

The heart has reasons that reason cannot know.

The human heart is a meadow full of fireflies, a summer western sky of shimmering distant lightnings, a shore set round with flashing lighthouses, far-away voices calling that we cannot understand.

The human heart is a tangled wood wherein no man knows his way.

The secrets that may be buried with a human heart.

The heart has its reasons which reason knoweth not.

But who can fathom the subtleties of the human heart? Certainly not those who expect from it only decorous sentiments and normal emotions.

A strange thing, the human heart in general, and woman's heart in particular.

the heart that one can see clearly, for the most essential things are invisible

The heart has its reasons which reason knows not of.

The heart has its reasons which reason knows not.

The heart has its own reasons that reason can't understand.

The human heart is a band playing in a park at a distance; we see the crowds listening, but we catch but fragments of the music now and again, and cannot make out the tune.