A wonderful fact to reflect upon, that every human creature is constituted to be that profound secret and mystery to every other. A solemn consideration, when I enter a great city by night, that every one of those darkly clustered houses encloses its own secret; that every room in every one of them encloses its own secret; that every beating heart in the hundreds of thousands of breasts there, is, in some of its imaginings, a secret to the heart nearest it!

Something of the awfulness, even of Death itself, is referable to this. No more can I turn the leaves of this dear book that I loved, and vainly hope in time to read it all. No more can I look into the depths of this unfathomable water, wherein, as momentary lights glanced into it, I have had glimpses of buried treasure and other things submerged. It was appointed that the book should shut with a spring, for ever and for ever, when I had read but a page. It was appointed that the water should be locked in an eternal frost, when the light was playing on its surface, and I stood in ignorance on the shore.

From “A Tale of Two Cities” by  Charles Dickens

In this snippet, Charles Dickens stands in awe as he contemplates the human being’s impenetrability.  Each person lives in her or his internal unknown world: “Every human creature is constituted to be that profound secret and mystery to every other. A solemn consideration, when I enter a great city by night, that every one of those darkly clustered houses encloses its own secret.”

One of the greatest geniuses of the world literature, Dickens displays his poetic sensitivity to reach into the deepest chambers of our mind. We will never be able to understand one another completely. It is a defense mechanism for human survival.