This liturgical meditation is take from Guardini's book, Sacred Signs.

We long for union with God, and we must so long, for it is our inmost need. Our soul points out two ways of obtaining this: they are different ways, but both reach the same goal.

The first way to union goes by knowledge and love.

Knowledge is a union: by knowing things we penetrate them and draw them into ourselves; they become our own, a part of our life. So also all love is union – not a mere striving, but in itself a union. So far as a man loves something, so far doe it already belong to him.

This union is, however, of a special kind: we express this by saying that it is ‘spiritual.’

Yet this word does not fully say all, for the other union, of which we shall speak later, is also spiritual. What we mean is that this union is one not of being, but of motion; of consciousness and frame of mind.

Is there any outward form for this – a likeness? Certainly, and a very wonderful one – light and heat.