Imponderable (adjective)

1. Too difficult or complex to be weighed, measured, or calculated; beyond calculation.
2. Not able to be influenced or affected by reason or calculation.

Origin:

From im- + ponder + -able, from latin pondus (weight), from pondere (to weigh).

Examples:

1. The imponderable nature of love made it difficult for the poet to put into words.
2. The imponderable forces of the universe were a mystery to the scientist.
3. The imponderable essence of life was the focus of the philosopher's inquiry.
4. The imponderable value of the rare artifact made it difficult to put a price on it.
5. The imponderable qualities of the leader made him difficult to predict or understand.