What is the difference between if and if-then?

Question

According to [33]. Davis, W. (1983). Weak and strong conditionals. Pacific Philosophical Quarterly, 64(1), 57-71., there exist two versions of if conditional as shown below.

(1) a. If it is humid, the TV will work.
b. If it is humid, then the TV will work. (Davis 1983)

(2) a. If you develop something complicated, you need complicated people.
b. If you develop something complicated, then you need complicated people.

In (1)a, the reading is that the humid condition does not effect the TV's work, while in (1)b, there exists the unknown connection between the humid condition and the TV's work. I don't know whether this effect also occurs in (2). Is this weak vs. strong effect pervasive or just limited to the case of (1)?

Answer 1

There is no widely successful account, in linguistics or in philosophy, which gives distinct truth conditions for conditionals with and without then—Davis (1983) notwithstanding.

In contrast, a widely held view that Davis was arguing against has been overturned since he was writing. He observed (p.57):

It is generally assumed that “then” is a redundant part of conditionals, that “If A, C” and “If A, then C” are synonymous.

The paper which largely overturned this view, influential in both philosophy and linguistics, is Iatridou (1993) On the contribution of conditional then.

According to Iatridou, If P, then Q carries the presupposition that in at least some Not P cases, Q will also not be true. So we are most likely to use then when we would not expect Q to happen unless P.

Because not all instances of If P, Q carry this same presupposition, so the story goes, it is possible to find sentences in which then will be infelicitous:

(1) ?Even if my leg falls off, then I will make it to your wedding.

There are various reasons why one might disagree with the arguments set forth in Iatridou (1993), not least because many of the grammaticality judgements therein are highly debatable. However, it does seem intuitive that the use of then might have a slightly contrastive effect. The use of the If P, Q construction already sets up P as a background for a Q eventuality. In other words it is widely agreed that If P, Q already means something like In the case of P, Q. The use of If P, then Q is then a bit like saying In the case of P, in that case Q, where the effective contribution of the truth-conditionally redundant then is to pick out P backgrounds in contrast with other ones. Though, as stated, that's just intuition.

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^{Interestingly, Iatridou states in her opening line (p.171):}

^{It is widely assumed that the appearance of then in a conditional is optional and that it contributes nothing to the meaning of the conditional as a whole 1}

^{That superscript 1 at the end of the sentence directs to the following footnote:}

^{The only exception that I know of is found in the philosophical literature, Davis (1983).}

^{So it seems as though Iatridou did not manage to find anyone converted to the Davis (1983) account either.}