But whoever keeps his word, God's love has most assuredly been perfected in him. This is how we know that we are in him:
Hereby we know that we are in him ...  Although the grammatical structure makes "God" the antecedent of "in him" in this place, still the meaning is "in Christ," no man ever having been "in God" by any other means than that of his having been baptized into the spiritual body of Christ.  Being "in God" and "in Christ" are exactly one and the same thing.  This thought comes to the foreground a number of times in this letter.  Thus John placed the same importance and priority upon this conception that are given to it in the writings of the apostle Paul who used the expression "in Christ" or its equivalent some 169 times.  The idea of the corporate body of Christ was not developed either by Paul or by John but is derived from the Lord himself who gave the foundation of it in such teaching as that of his being the vine, the apostles being the branches, and all Christians abiding "in him," that is, "in the true vine" (John 15).  Since one enters "him" through primary obedience (baptism), it is the true continuity of that holy relationship that John here declared us to "know" if we keep his word.