Closely associated with faith is Paul’s doctrine of the Holy Spirit. The word itself (πνεῦμα) was intelligible to both the Greek and Jewish world, but since Paul was not a systematic theologian, it is a matter of much dispute as to what his exact concept of the Holy Spirit was. He evidently thought of the Spirit as a divine objective reality. In some passages he identifies Christ and the spirit of Christ or the spirit of God;[316] from this we may conclude that he probably thought the Holy Spirit to be a mode of the indwelling Christ. But if his concept is not clear to us, we have no difficulty in understanding his ideas as to the operation of the Spirit. He taught that it is the Spirit which assures men of their sonship so that they may address God as their Father; that it transforms the inner man; and that it demands the sanctification of the body, for the body is the temple of the Holy Spirit.[317] From the Spirit come the fundamental virtues—“love, joy, peace, long-suffering, kindness, goodness, faithfulness, meekness, temperance.”[318] Thus the Spirit is the means of continuing the believer in his course and of perfecting him in the Christian life. In common with his contemporaries Paul of course believed that many ecstatic phenomena—speaking with tongues and prophesying, for example—were the gifts of the Spirit; but his instructions to the excitable Corinthians show his good sense and wisdom.[319] In all his teaching Paul was highly practical. It is not certain that he held a dualistic view of man’s nature in the Greek or Persian sense, but he was well acquainted with the struggle between man’s lower and higher natures and he knew the warring elements within the individual. He frequently contrasted the flesh and the spirit, meaning by the first man’s sinful nature which keeps him in the bondage of wickedness. From this bondage and consequent death he held that man cannot escape by his own powers; but that Christ delivers man from sin and its consequences. This deliverance is an act of grace, a gift from God. We have only to read the Epistles which bear his name to see how wisely he dealt with actual errors and sins, or stirred to concrete acts of righteousness the members of the churches which he had founded. In most of his writing Paul dwelt on the present salvation which the mystic union with Christ secured, but at times he treated the eschatological nature of salvation, teaching that the full effects of it would be realized when Christ should come to be glorified in his saints. That this day would come quickly the apostle fully believed; then the faithful, dead and living alike, would receive their full reward and the wicked their punishment.