On the other hand he writes, “We worship the Father of the Truth, and the Son who is the Truth, being in subsistence (τῇ ὑποστάσει) two Contra Celsum, viii. p. 386..”  On this passage Bishop Bull remarks:  “The words ὑπόστασις and οὐσία in ancient times were variously used, at least by the Christians.  That is to say, sometimes ὑπόστασις was taken by them for what we call οὐσία, and vice versa, οὐσία for what we call ὑπόστασις:  sometimes the ancients even before the Council of Nicæa used ὑπόστασις for what we now call ‘person’ or ‘subsistence Def. Fid. Nic. II. c. 9, § 11.’.”  This Bishop Bull presently explains again as “an individual thing subsisting by itself, which in rational beings is the same as person.”