Let us remember that this doctrine is not in the New Testament, but is an attempt to explain certain experiences that are ascribed in the New Testament to Jesus, the Father, the Holy Spirit. Even the hardiest thinkers caution us that our knowledge of God is limited to a knowledge of His relations to us: Augustine says, "the workings of the Trinity are inseparable," and Calvin, commenting on a passage whose "aim is shortly to sum up all that is lawful for men to know of God," notes that it is "a description, not of what He is in Himself, but of what He is to us, that our knowledge of Him may stand rather in a lively perception, than in a vain and airy speculation." But let us also recall that in this doctrine generations of Christians have conserved indispensable elements in their thought of God:--His fatherhood, His Self-disclosure in Christ, His spiritual indwelling in the Christian community. Wherever it has been cast aside, something vitalizing to Christian life has gone with it. But at present it is not a doctrine of much practical help to many religious people; and it often constitutes a hindrance to Jews and Mohammedans, and to some born within the Church in their endeavor to understand and have fellowship with the Christian God. We may adopt one of two attitudes towards it: we may accept it blindly as "a mystery" on the authority of the long centuries of Christian thought, which have used it to express their faith in God--hardly a Protestant or truly Christian position which bids us "Prove all things; hold fast that which is good"; or we may consider it reverently as the attempt of the Christian Church of the past to interpret its discovery of God as the Father Lord, revealed in Christ, and active within us as the Spirit of love; and use it in so far as it makes our experience richer and clearer, remembering that it is only a man-made attempt to interpret Him who passeth understanding. The important matter is not the orthodoxy of our doctrine, but the richness of our personal experience of God. Dr. Samuel Johnson said: "We all _know_ what light is; but it is not so easy to _tell_ what it is." Christians know, at least in part, what God is; but it is far from easy to state what He is; and each age must revise and say in its own words what God means to it. Here is a statement in which generations of believers have summed up their intercourse with the Divine. Have we entered into the fulness of their fellowship with God?