The exact context may make a difference, but on average I think the most common term would be...
implementation - the realization of an application, or execution of a plan, idea, model, design, specification, standard, algorithm, or policy.
It's a particularly common usage in computer science and the IT industry, but it's also perfectly suitable in the context of government policies, etc.
That's why good style encourages using positive instead of double negative clauses... and the quotes only confuse the matters more by separating the expression from the sentence it applies to.
‘but for’ his or her act the harm would not have happened.
this could be rephrased, by removing the double negative, as
only due to his or her act the harm would have happened.
And in this context the becomes quite clear.
the defendant can be said to have caused a result only if [only due to his or her act the harm would have happened.]
I guess the writer tried to avoid the repetition of 'only', and as result made this quite hard to comprehend.
"A is only true if only X is true." so, there are factors X,Y,Z and for the conclusion A to be true, X must be true, while Y and Z must be false. In all other cases A is false.
got transliterated as
*"A is only true if [if not for X being true, all factors would be false]"
...and phrased it with awkward punctuation and rare and unintuitive use of but.
A stylistically better and clearer phrasing would switch the phrases around a bit and add both variants of outcome:
the defendant can be said to have caused a result only if the harm would have happened due to his or her act, and not for any other reasons.
Best Answer
In your quote, the meaning of provide for is to act to prepare for something (Wiktionary, verb sense 2).
We may rephrase the quotation this way:
Let's look at an example sentence:
If you substitute provide in the place of provide for:
the resulting sentence is absurd: stronger abutments are somehow supposed to invoke storms.