Incapable of being analyzed, investigated, or scrutinized; impenetrable, not easily understood; unfathomable; mysterious, as in an inscrutable smile; incapable of being seen through, as in the inscrutable depths of the ocean.
We have as yet hardly spoken of the infant: that little creature, whose innocent life had sprung, by inscrutable decree of Providence, a lovely and immortal flower, out of the rank luxuriance of a guilty passion. How strange it seemed to the sad woman, as she watched the growth, and the beauty that became every day more brilliant, and the intelligence that threw its quivering sunshine over the tiny features of this child! Her Pearl!—for so had Hester called her; not as a name expressive of her aspect, which had nothing of the calm, white, unimpassioned lustre that would be indicated by the comparison. But she named the infant “Pearl,” as being of great price—purchased with all she had—her mother’s only treasure!
—Nathaniel Hawthorne The Scarlet Letter (1850)