[For Paul] everything always ends in Christ and with Christ. He is the final point, He is the explanation of Paul's living and his whole outlook upon life ... Christ is all-sufficient for every circumstance, for every eventuality and for every possibility ... he is introducing us to what in many ways we may describe as the cardinal New Testament doctrine. The Christian life ... is not just a philosophy, it is not just a point of view, it is not just a teaching that we take up and try to put into practice. It is all that, but it is something infinitely more. The very essence of the Christian life, according to the New Testament teaching everywhere, is that it is a mighty power that enters into us; it is a life, if you like, that is pulsating in us. It is an activity, and activity on the part of God ...
[Christians] are not just men who have taken up a certain theory and are trying to practise it; it is God doing something in them and through them ... our highest thoughts, our noblest aspirations, our every righteous inclination is from and of God, is something that is brought into being in us by God Himself. It is God's activity and not merely our activity (Philippians 3: 10) ... You find [Paul] saying exactly the same thing in other Epistles (Ephesians 1:19, 20; 2:10) ... You remember also the great statement at the end of the third chapter: 'He is able to do exceeding abundantly above all that we ask or think, according to the power that worketh in us'.
Now, that is typical and characteristic New Testament doctrine, and if we have not grasped it we are surely missing one of the most glorious things about the Christian life and position ... We come back again to what I am never tired of quoting, namely, John Wesley's favourite definition of a Christian. He found it in that book by Henry Scougal ... The life of God in the soul of man ... The Christian is not just a good, decent, moral man; the life of God has entered into him, there is an energy, a power, a life in him and it is that that makes him peculiarly and specifically Christian.
~Martyn Lloyd-Jones, Spiritual Depression, pp. 291-2