Let us think seriously this afternoon of one word; the word which is the key-note of this psalm. A very short word; for in our language there is but one letter in it. A very common word; for we are using it all day long when we are awake, and even at night in our dreams; and yet a very wonderful word, for though we know well whom it means, yet what it means we do not know, and cannot understand, no, nor can the wisest philosopher who ever lived; and a most important word too; for we cannot get rid of it, we cannot help thinking of it, cannot help saying it all our life long from childhood to the grave. After death, too, we shall probably be saying that word to ourselves, each of us, for ever and ever. If the whole universe, sun, moon, and stars, and all that we ever thought of, or can think of, were destroyed and became nothing, that word would probably be left; and we should be left alone with it; and on what we meant by that little word would depend our everlasting happiness or misery. And what is this wonderful little word? What but the word I? Each one of us says I--I think, I know, I feel, I ought, I ought not, I did that, and cannot undo it: and why? Because we are not things, nor mere animals, but persons, living souls, though our bodies are like the bodies of animals, only more perfect, that they may be fit dwelling-places for more perfect souls. The animals, as far as we know, do not think of themselves each as I. Little children do not at first. They call themselves by names by which they hear others call them: not in the first but in the third person. After a while there grows up in them the wonderful thought that they are persons, different from any other person round them, and they begin to say--I want this, I like that. I trust that I shall not seem to you as one who dreams when I say that I believe that is a revelation from God to each child, and just what makes the difference between him and an animal; that God teaches each child to say I; to know that it is not a mere thing, but a person, a living soul, with a will of its own, and a duty of its own; responsible for itself; which ought to do some things, and ought not to do other things. And what a solemn and awful revelation that is, we shall see more clearly, the more we think of it.