And so, too, when the youth calls for further proof of the "Nameless," the Sage reminds him that there are universally acknowledged truths incapable of formal proof. The thought which the poet here dwells upon is similar to Cardinal Newman's teaching in the _Grammar of Assent_, though Tennyson's use of words does not here, as elsewhere, harmonize with Catholic doctrine. There are truths, the knowledge of which is so intimately connected with our own personality, that the material for complete formal proof eludes verbal statement. We reject, for example, with a clear and unerring instinct, the notion that when we converse with our friends, the words and thoughts which come to us proceed possibly from some principle within us and not from an external cause, and yet it is not a matter on which we can offer logical proof. The same sensations could conceivably be produced from within, as they are in a dream. Logical proof, then, has (so the Ancient Sage maintains) to be dispensed with in much that is of highest moment: Thou canst not prove that thou art body alone, Nor canst thou prove that thou art spirit alone, Nor canst thou prove that thou art both in one: Thou canst not prove thou art immortal, no Nor yet that thou art mortal--nay, my son, Thou canst not prove that I, who speak with thee, Am not thyself in converse with thyself, For nothing worthy proving can be proven, Nor yet disproven. And close upon this follows the beautiful passage in which the hopeful and wistful upward gaze of faith is described. While melancholy and perplexity constantly attend on the exercises of the speculative intellect, we are to "cling to faith": She reels not in the storm of warring words, She brightens at the clash of "Yes" and "No," She sees the Best that glimmers thro' the Worst, She feels the Sun is hid but for a night. She spies the summer thro' the winter bud, She tastes the fruit before the blossom falls, She hears the lark within the songless egg, She finds the fountain where they wailed "Mirage"!