Propositional logic and the future

If/then thinking is always based (to a real degree) on an assumption. It's akin to risk assessment, the validity of the 'then' always has to be proven beyond a reasonable doubt. That's where it gets tricky and logicians (and scientists for that matter) engage in varying degrees of willing suspension of disbelief to underscore a hypothesis.

I think it should be regarded as a speech act rather than just a truth apt declaration. If someone actually says that, it's got a certain set of illocutionary forces (hopeful, determined...). The material conditional alone does not.

Maybe another way of seeing this would be to assume it could be translated to the material conditional. Then an equivalent translation would be the transposition. (A => B) <=> (¬B => ¬A), which would yield "Not(McDoodle will get a distinction in his exam) if Not(McDoodle works hard)", I'd like to say this is equivalent to "McDoodle won't get a distinction in his exam if he doesn't work hard", which has a different set of illocutionary forces (threatening, frustrated).

Whether it's appropriate to say the translation to the material conditional isn't possible because it does not preserve (expected?) illocutionary forces (IE the logical validity of the argument I just made) is up in the air.

Edit: though this doesn't deal with the relationship between indicative conditionals and causes, so disregard post if uninteresting or irrelevant.

Propositional logic has no mechanisms for tense. Of course it would be possible to translate the antecedent and consequent with the tense already folded into them. Thus if A = "McDoodle will work hard" and B = "McDoodle will get Distinction on his exam," then A--> B would mean that there is no possible situation in which you will work hard, but that you won't pass the exam. On some readings of the sentence, that is more or less an adequate translation. There is no 'time' at which one validates truth of propositions in propositional logic -- there is simply an interpretation function that brutely assigns true or false to every letter. If you wanted, you could assume that that function is in effect representing evaluation from a single point in time.

I will take fdrake's ideas for when I create my ideal logic, and meanwhile accept the brute truth of TGW.
It feels intuitively weird though that propositional logic is not, in effect, shaped for evaluation.

For sake of argument, let's assume there is no such thing as retro-causality, such that a person's entire behaviour is explainable as being caused by events of the past.

Then whenever a person plans on, predicts, or discusses the future, what is it that justifies our interpretation of his behaviour as being of the actual future?

Suppose it is Monday and that he predicts the Sun will rise tomorrow on Tuesday. Given that it is currently Monday, can his prediction currently refer to Tuesday, before Tuesday has actually happened?

Or does it only make sense retrospectively, in a post hoc fashion, after having witnessing the following morning of Tuesday, to identify his earlier prediction as referring to the dawn of Tuesday?

Reply to mcdoodle What a coinidence! I have the same doubt. I'm not taking a course but reading introductory books on logic.

[B]P = If McDoodle works hard, he will get Distinction in his exam.[/b]

P can be translated into the material conditional because the truth functional interpretation involves ALL possible worlds. That's why it doesn't matter that P is about the future. What do you think?

Quoting TheMadFool

What do you think?

It's a couple of years on. And McDoodle did get his distinction!

My view now is: the ordinary logical form does not and cannot accurately reproduce the sentence-meaning. It makes an entirely different statement. That in a way is the point of Wittgenstein's shift from the Tractatus view to the Investigations view: most 'propositions' are judgments, not statements of fact. What is the logic of judgments?

Maybe there is a form of logic that can render the sentence in logical form, but I don't know enough about Logic to know what that would be. In ordinary language, it also matters who is saying P, and to whom: any 'logical' interpretation will have difficulty covering all the bases and will have to make assumptions about 'context'. It might be for instance spoken by someone who knows McDoodle is a lazy arse so is certain not to get a Distinction: how is that covered? 'Other things being equal' has to be brought into action here :)

Reply to mcdoodle From what I've read, the point of logic is to capture only those elements in a sentence that have logical import. In your statement "P = If McDoodle works hard, he will get Distinction in his exam.", the only logically pertinent thing is the sufficient-necessary connection between "McDoodle works hard" and "he will get Distinction in his exam". So, why can't this be captured by the material conditional? I can see that we'd have to wait to decide the truth value of the consequent (McDoodle gets a Distinction in his exam) but that doesn't hamper the material conditional interpretation.

Quoting mcdoodle

My view now is: the ordinary logical form does not and cannot accurately reproduce the sentence-meaning. It makes an entirely different statement. That in a way is the point of Wittgenstein's shift from the Tractatus view to the Investigations view: most 'propositions' are judgments, not statements of fact.

But if the meaning of future-contingent propositions are their use, then before the future has arrived they are reducible to the assertion or denial of present behavioural dispositions.

Only upon expiry of the future-contingent state of affairs that they are, post-hoc, associated with, can those propositions be retrospectively interpreted as being of the associated state of affairs they "pretended" to be about at the original time of their assertion.

hence those sentences are surely truth apt, both now and in the future, albeit for different reasons, and propositional logic should capture that relationship succinctly.

Quoting TheMadFool

From what I've read, the point of logic is to capture only those elements in a sentence that have logical import

But what then do we do with what's left over? There will always be some surplus of meaning left behind in ordinary language which logic hasn't captured. Logic, then wouldn't provide a translation, nor an interpretation, but a narrowing of meaning.

Quoting sime

But if the meaning of future-contingent propositions are their use, then before the future has arrived they are reducible to the assertion or denial of present behavioural dispositions.

The Wittgenstein line is that the meaning of *words* is mostly their use. Propositions are a different kettle of fish, surely. A future-contingent proposition is a sort of judgment. Actually I don't think it becomes 'false' if McDoodle doesn't in the fullness of time get his distinction: they are judgments at the time they were made. As TGW said earlier in the thread, logic is timeless in this setting.

Quoting mcdoodle

But what then do we do with what's left over? There will always be some surplus of meaning left behind in ordinary language which logic hasn't captured. Logic, then wouldn't provide a translation, nor an interpretation, but a narrowing of meaning

I think the worst part is, as you say, logic can't grasp the entire content of a sentence in natural language. The best part is, logicians are cognizant of this shortcoming.

Another point is that, may be these other aspects of language aren't so much of a problem (like I've been saying).