But it is by no means clear that "mind" in I Cor. ii. 16b is the same as "spirit." If a man has the Spirit of Christ, he also has the mind of Christ; the Spirit gives him an understanding of the thoughts of Christ. Conversely, the possession of the mind of Christ is a proof that the man has the Spirit of Christ; it is only the Spirit who could have given him his understanding of Christ's thoughts. But it does not follow by any means that the term "mind" means the same thing as the term "spirit." Moreover, the passage is entirely isolated; and the choice of the unusual word "mind" may be due to the form of the Septuagint passage which Paul is citing. At any rate, the plain fact is that the terminology in Hermes Trismegistus and related sources is strikingly different from that of Paul. Reitzenstein finds himself in the peculiar position of proving that Paul is dependent upon pagan sources by the fact that the Pauline terminology does not occur in the pagan sources. It will not do for him to say that the terminology is of little importance and that the ideas of Paul, if not the terminology, are derived from the pagan mysteries. For it is just Reitzenstein who insists upon the importance of words as the vehicle of ideas. His fundamental argument is that Paul used the terminology of the mystery religions, and with the terminology received also the ideas. It is therefore important to observe that Reitzenstein's lexical parallel utterly breaks down. But if the Pauline doctrine of the Spirit was not derived from the pagan mystery religions, whence was it derived? The answer is perfectly plain. It was derived ultimately from the Old Testament.[207] Unquestionably, indeed, it goes far beyond the Old Testament, and the enrichment of its content may conceivably be explained in various ways. The Gospels and Acts explain the enrichment as due partly to the teaching of Jesus Himself and to the coming of the Spirit on the day of Pentecost. This explanation will be rejected for the most part by naturalistic criticism. Paul explains the enrichment as due partly to the experience which he had of the presence of Christ. This explanation is regarded as no explanation at all by the school of comparative religion. But it is not necessary in the present connection to discuss these matters. All that needs to be observed now is that the basis for the Pauline doctrine of the Spirit is found in the Old Testament. [207] Bousset (_op. cit._, p. 141, Anm. 2) admits that the terminology of Paul, especially his use of the term "Spirit" instead of "mind" and his use of the terms in the contrast between "Spirit" and "flesh" may possibly be due partly to the Old Testament, but insists that such terminological influence does not touch the fundamentals of the thought. Such admissions are important, despite the way in which Bousset qualifies them.