Firstly, it need hardly be said that Mr R never meant Christ was a myth! Accusation of such a blasphemous statement on page 2 is totally uncalled for.
Eternal life was something that the Jews looked forward to (Ps. 133.3; Dan 12.2; Luke 10.25), and to be entered into for both Israel and the saved of the nations in the world to come, the coming age. (Matt. 25.46). That is one side of the matter.
On the other, eternal life is not the indefinite extension of human life even if achievable by keeping the Law (Lk. 10.25-28). It is set forth objectively in Christ (1 Jn. 5.20). It is given to everyone now believing on Him, the Son of God (Jn. 3.16). But it is in Him, the Son, not simply in the believer (Jn. 5.11-12).
Quoting from another, "We may remark, that in every case the Lord brings in the cross. It was the only passage from this world of nature, to a world of glory and of eternal life." (J N Darby, Synopsis of the books of the Bible, Volume 2, page 181.) Hence, at least in this aspect, a "sphere" it might be said. Again, "Eternal life, although received now, was, in possession and enjoyment according to God's purpose, on the other side of the cross." (Ibid.)
The main point in the second part "ON RIGHTEOUSNESS" to which CS takes exception is that “Divine righteousness is to be displayed in us in Christ.” (Italics CS.)
As said by another elsewhere, “We have to remember that, at our appearing before the judgement-seat of Christ, we are already glorified.” (J N Darby, Synopsis of the books of the Bible, Volume 4, page 234. Italics JND)
And, “When the Christian is thus manifested, he is already glorified, and, perfectly like Christ, has then no remains of the evil nature in which he sinned.” (Ibid, page 229.)
And again, “God had made Him who knew no sin to be sin for us, in order that we should be made the righteousness of God in Him. This was the true way to reconcile us, and that entirely, to God, according to the perfection of God fully revealed. For He had set His love upon us where we were, giving His Son, who was without spot or motion or principle of sin; and making Him (for He offered Himself to accomplish the will of God) sin for us, in order to make us in Him – who in that condition had perfectly glorified Him – the expression of His divine righteousness, before the heavenly principalities through all eternity; to make us His delight, as regards righteousness; “that we should be the righteousness of God in him.” Man has no righteousness for God: God has made the saints in Jesus, His righteousness. It is in us that this divine righteousness is seen fully verified – of course in Christ first, in setting Him at His right hand, and in us as in Him. Marvelous truth!” (Ibid, page 234. The italics mine - MB.)