On What We Can Ensure (B. Schnieder)

Synthese 162 (2008), 101115.

Abstract: The Conjunction Principle says, roughly, that if the truth of a conjunction can be brought about, then the truth of each conjunct can be brought about. The current essay argues that this principle is not valid. After a clarification of the principle, it is shown how a proper understanding of the involved notions falsify the principle. As a corollary, a recent attack on van Inwagen’s Consequence Argument will be rebutted, because it relies on the invalid conjunction principle.


  1. Hi,

    I thought the falsity of the conjunction principle was fairly routine in logics for “bringing it about that”. The standard story is that if I can bring it about that my hand is up, I can bring it about that both my hand is up and T (“T” the verum); but I can’t bring it about that p or -p, that’s settled and has nothing to do with my agency. Typically, BAp -> BA(p v T) is thm, often derived from the NO principle, ~BAT as axiom. It’s built into the negative conditions from Porn’s early work inthe 70s, and in most formal accts of agency operators ever since (Chellas was an exception).



  2. Oh dear, it seems I just didn’t know that branch of literature. I argue against the Conjunction Principle with exactly the sort of example you mention (except that I do not use a logical truth but a mathematical truth, namely 2+2=4; since I can raise my hand, I can render it true that my hand rises & 2+2=4).
    My only excuse for thereby merchandising stale news is that neither did I know that the principle had been discussed in the literature you mention, nor did the people in the debate that I was engaging in.

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