Yes, I’m quite familiar with “The Practice of Substituted Love”, or rather with the chapter by that title in Charles Williams’s He Came Down from Heaven, which (I agree) is one of this Oxford Inkling’s most distinctively compelling pieces. I say “rather” because I’ve never myself actually engaged in a “contractual” substitution. Though Williams doesn’t use this adjective, it seems a good shorthand way of underscoring what he does say about the necessity of both parties entering into a formal agreement as to what precisely is being set down by the one and picked up by the other.
In praying for people, I’ve sometimes imaginatively tried to place myself in their shoes—as I’m sure you have too—but that’s at most only half of the substitution Williams has in mind. As for great saintly intercessors like St John of San Francisco, they obviously went way beyond anything we’re capable of in bearing the burdens of others, but here too I would be surprised if they entered into quite the formal agreement Williams intends. From what I know of St John, he would have simply left it to God to orchestrate whatever mystical “co-inherence” was required.
This is not to say, however, that Williams’s advice isn’t valid or valuable. On the contrary, it has always made excellent sense to me, at least in principle, and we have no less than C. S. Lewis’s testimony that Williamsian substitutions do truly work. (Lewis claimed he was able to give his wife some relief when she was battling with cancer by taking her pain into his own body.) But I don’t myself have any direct, experiential evidence as to how it works, and for that reason I’m wary about presuming too much in trying to answer your questions, particularly when it comes to the issue you raise about “degree”—that is, exactly how much it’s safe to take on.
Obviously one answer would be: no more than you can really handle! But this just begs the question, I realize, since until you’ve actually attempted to practice substitutionary love, you aren’t going to know how much may be too much. One thing I can say with certitude, however: It’s never appropriate to lay prudence aside, for there is nothing unreasonable about “our life in Christ”; theosis makes a man more, not less, logical and discerning. As Williams specifies:
“It is necessary (a) not to take burdens recklessly; (b) to consider exactly how far any burden, accepted to the full, is likely to conflict with other duties. There is always a necessity of intelligence.”
If I were in your shoes, I believe I would conduct a test. First, of course, you should make a point of explicitly asking Christ and the Panagia for their protection and blessing, telling them of your wish to be helpful to your friend but of your understandable doubts as to how best to proceed.
Guided and guarded by these prayers, the test would involve some careful reflection concerning the degree to which you’ve already been bearing E.’s burden simply by talking with her. Anytime we listen to a friend’s troubles—acting as a “sounding board” if nothing else—there is at least the beginning of a Williamsian contract. For in being open with you about her suffering, she has already implicitly asked you to bear a portion of her burden, and you’ve clearly accepted that.
Here are some questions to ask yourself based on this experience: Have these conversations been of any real and lasting help to her? If so, what tangible form has the benefit taken? How have you felt afterward? Have her depression and sadness and feelings of guilt left a lasting impression on you? Did you wake up the next day feeling depressed or sad or guilty? If so, how long did the feeling last? How much “room” did the feeling take up in your heart, or (if you prefer) how much did it “weigh” on your soul? Was it something you could watch more or less objectively, or did it affect (and perhaps infect) your whole state of mind?
I could go on, but you see the line of my questioning. The point would be to try to get a sense of what your spiritual “muscles” are capable of. If you can pick up 50 pounds pretty easily, then you have good reason to think you can pick up 60 without straining yourself, whereas 100 might be too much too soon. I realize that finding a trustworthy scale, appropriately calibrated in “spiritual pounds”, isn’t going to be easy!
Obviously this isn’t the whole story. If at the end of this self-examination, by extrapolating from your past conversations with E., you believe you have the necessary strength to move from 50 to 60 “pounds” of her burdens, then you’ll need to speak to her specifically about the possibility of substitution. At which point the question becomes: What will she make of this idea? Would she believe such a “contract” could work, or would it strike her as merely weird? How seriously does she take the idea of the Church as Christ’s body? Does she understand the “communion of saints”?
Unless she is a priori open to these teachings—unless, in short, she has at least some faith in the “mystical” dimensions of Christianity—she will probably not be able to enter wholeheartedly into the Williamsian “web of exchange”, and if she can’t do that, she isn’t going to be able to give up her burden in a meaningful and potentially operative way. As Williams repeatedly emphasizes, she must be just as willing to put down as you are to take up:
“The one who gives has to remember that he has parted with his burden, that it is being carried by another, that his part is to believe that and be at peace.”