One of my biggest peeves is when the active/passive obedience of Christ is described in this way:
Active obedience has in view his obedience to the moral law, so that wherever there is such obedience, it is active obedience. And likewise passive obedience has in view his obedience of suffering, so that wherever such obedience is found it is passive obedience.
This is inadequate, imprecise, and doesn’t get at what we’re really talking about when we speak of Christ’s active and passive obedience. Some other posts here are already operating on the assumption that such definitions are imprecise (e.g. https://brandoncorleyschoo.wixsite.com/brandoncorley/post/justification-as-right-to-eternal-life-more-than-forgiveness), but I thought it would be good to create this post in order to make this explicit.
A more accurate definition, is that in relation to Christ:
Active obedience is covenantal obedience in meritorious relation to a reward. Passive obedience is obedience in relation to penal satisfaction (and thus a discharge of penal debt).
Because of this:
Adam could have merited eternal life by suffering and though there would be suffering, this would not be passive obedience since it holds no relation to a discharging of penal debt. Likewise, Christ could have discharged our debt of sin through an obedient death and though there would be obedience, even covenantal obedience, this would not be active obedience since it would hold no relation to a reward beyond the discharging of penal debt (ie God could have sent the Son to die for our sins and yet not to merit Heaven for us). Of course, this also allows us to say that Christ merited Heaven for us even by his death as his suffering may be considered as active obedience.
The active and passive obedience of Christ are inseparable then, not in themselves, but by the covenant constitution of God. Each are formally distinguished by the ends that they have in view and procure, not by the manner in which they procure those ends as such. If an action has a relation to ex pacto meriting a reward (of course, not considering the discharge of penal debt as a reward), it is active obedience. If an action has a relation to satisfying a penal debt, it is passive obedience. The mode is irrelevant.
Addendum: It might be asked which logically comes first in the order of application to us. I know it is often said that the imputation of Christ’s obedience precedes the remission of sins, but when this is said, Christ’s obedience is being considered as a whole, including in it both active and passive obedience (though of course it's only true formally and strictly because of passive obedience alone). In this sense, of course it’s true that the imputation of His obedience must precede the remission of sins. But if it is asked only whether our sins are first remitted or we are first given the right to life, it seems to me we must answer that our sins our first remitted and then we are given the right to life. In that sense, in the logical consideration of things, Christ’s passive obedience precedes his active obedience in their imputation to us. The reason for this is because we have first fallen into sin and thus have a claim of penal debt hanging over us before we are given the right to life through Christ. Yet one cannot have both the right to eternal life and the debt of eternal death at the same time since they are incongruent with each other. The very order of redemption shows that this is so in application since man is granted the right to eternal life not as he is in a state of pure nature, but as he is fallen.