The belief in the impotence of intellectual knowledge is very closely connected, it is indeed based, upon these “gleams” of ecstasy.  The prologue to In Memoriam (written when the poem was completed) seems to sum up his faith after many years of struggle and doubt; but it is in the most philosophical as well as one of the latest, of his poems, The Ancient Sage, that we find this attitude most fully expressed.  Tennyson wrote of it:  “The whole poem is very personal.  The passages about ‘Faith’ and ‘the Passion of the Past’ were more especially my own personal feelings.”  Through the mouth of the Sage, the poet declares in impassioned words the position of the mystic, and points out the impotence of sense-knowledge in dealing with that which is beyond either the senses or the reason: 

    For Knowledge is the swallow on the lake
    That sees and stirs the surface-shadow there
    But never yet hath dipt into the abysm.

Tennyson, like Wordsworth, emphasises the truth that the only way in which man can gain real knowledge and hear the “Nameless” is by diving or sinking into the centre of his own being.  There is a great deal of Eastern philosophy and mysticism in the Ancient Sage, as, for instance, the feeling of the unity of all existence to the point of merging the personality into the universal.

    But that one ripple on the boundless deep
    Feels that the deep is boundless, and itself
    For ever changing form, but evermore
    One with the boundless motion of the deep.

We know that Tennyson had been studying the philosophy of Lao-Tsze about this time; yet, though this is, as it were, grafted on to the poet’s mind, still we may take it as being his genuine and deepest conviction.  The nearest approach to a definite statement of it to be found in his poems is in the few stanzas called The Higher Pantheism, which he sent to be read at the first meeting of the Metaphysical Society in 1869.

Speak to Him thou for He hears, and Spirit with Spirit can meet—­
Closer is He than breathing, and nearer than hands and feet.

* * * * *

And the ear of man cannot hear, and the eye of man cannot see;
But if we could see and hear, this Vision—­were it not He?

In William Law, Burke, Coleridge, and Carlyle, we have a succession of great English prose-writers whose work and thought is permeated by a mystical philosophy.  Of these four, Law is, during his later life, by far the most consistently and predominantly mystical.