A friend asked me the difference between Dispensationalism and and Covenant Theology. My answer is that the one stresses discontinuities between the Old and New Testament, while the other stresses continuity. That's a pretty vague statement, but I think it's a good place to start. Obviously both are -isms, and so both are definitely wrong in at least some points.
One of the effects of reading Darby extensively was that I began to back off a lot from the Dispensationalism I grew up with, as I began to see more and more continuities between the Old and New Testaments. That's not to say I dove into Covenant Theology, or anything like it. But reading Darby forced me to see and appreciate many continuities between the Old and New Testaments, which aren't really acknowledged among more mainstream Dispensationalists.
I really do believe all -isms are wrong. Dispensationalism, Calvinism, Arminianism – they're all wrong by virtue of the fact they're -isms. Yes, even Darbyism (and that really is a thing). They're all wrong because none quite addresses the whole counsel of God. Further, it seems like we humans just can't resist moving from "working model" to "interpretive framework" to "replacement for Scripture." We just can't seem to avoid getting to the place where we disregard at least some part of Scripture because of our personal theology (Matthew 15:1–6).
Don't get me wrong! If the choice is between Calvinism and Arminianism, and I have to choose, I'll take Calvinism every time. As far as I can tell, it represents Scripture much more completely and honestly than the other... but it would be far better for me to stick to Scripture. Similarly, I think Dispensationalism is a much better -ism than Covenant Theology, but it's still an -ism, it's still lacking, and it still easily becomes a replacement for Scripture if we allow our vigilance to fail.
I've said it many times: the unique feature of Darby's writings is that he resists the temptation to develop a theology. I wish I could do the same.
One of the marks of the "dispensationalism" of Darby, Kelly, et al. was the teaching that a godly walk isn't the result of careful adherence to the Law, or careful self-discipline, but the result of our union with Christ in His death, the indwelling Holy Spirit, and the work of God in us. Of course that's a mark of that era's Dispensationalism that was quick to disappear. Many who teach Dispensationalism today still mention our union with Christ, but they seem to think it's relegated to a "positional" truth, not something that really affects our lives.
Of course there is the opposite error: an error that I easily fall into. We won't passively fall into godliness. It's easy for me (and some other people I know) to allow ourselves to fall into the error opposite legalism, which is an almost fatalistic "passivism." That's not what Scripture teaches.
So what does Scripture teach?
Psalm 127:1–2 shows us what's happening behind the scenes. There are builders working on a house, but unless the Lord is the one actually building it, their labor is vain. There are watchmen watching over a city, but unless the Lord is keeping it, their waking is in vain.
Vain labor is a thing. It's probably more common than we realize: time, effort, resources spent pursuing some end on our own, without the Lord being in it. Robert has commented that "without me you can do nothing" (John 15:5) is a promise we don't like to remember. We like to think we are capable of accomplishing things on our own, we don't like to remember that without the Lord, we might well do things, but we can't accomplish anything.
Well, we don't interpret Psalm 127:1–2 to mean that the city shouldn't post watchers, nor that the builder of a house shouldn't work hard. That's going beyond what the Scripture actually says. It's not an injunction against human effort, but it is an observation that we cannot control the outcome of our labors. The Lord accomplishes what He sets out to accomplish, and we work against Him in vain.
We like to speak out against laziness – and rightly so –, but Psalm 127:2 tells us that the Lord gives rest to His beloved. Now, I read "His beloved" to mean primarily Christ, but it seems to me there is an extension to us here as well. When we recognize that our work is really His work, then we realize the outcome isn't really our concern. We don't pour our lives into vain labor, we allow Him the end that He wants.
At the same time, I have come to believe that our work (work "of the Lord" 1 Corinthians 15:58) is real and significant. I confess that any number of times over the last twenty-five years, I've held to a view pretty close to fatalism. I have many times believed – in fact, if not in words – that we are more or less just to sit and wait for God to do the work. I was wrong. That's not what Scripture describes. Rodger mentioned to me that sonship implies a significant relationship, almost an uneven partnership. We have been called into a relationship with the Father and the Son where we have been freed and empowered to take part in the work the Lord is doing.
But make no mistake, the partnership is definitely not an even one. That's what Psalm 127 is saying. Those who build the house are laboring: but it's the Lord who really builds the house. The watchmen are waking, but it's the Lord who is keeping the city. So we're not working to produce something for God. We're working with God, to be a very small part of what He's producing. That's really the idea of sonship: that we come into the family business and take part. But we don't delude ourselves into thinking the family business was struggling until we took part: God is and was getting precisely the outcome that He wants.