Why not?

Iâm not sure how simple process of elimination can be considered a logic puzzle. Guess it depends on your definition.

I think most things most people call logic puzzles involve using logic to eliminate options as part of the process of solving the puzzle.

I agree that process of elimination is often a key part of logic or logic puzzles. I just donât see how by itself that would constitute a logic puzzle.

Here is what I would mean by a logic puzzle, Iâve posted this before but it was a long time ago and I canât remember where or when. The surprise quiz problem:

On Friday near the end of class the Philosophy professor tells the class there will be a surprize quiz sometime next week, so they should study this weekend to make sure they are ready. One student raises his hand and says âwell we know it canât be on Friday, since if we havenât had it by Thursday at the end of class it would mean itâs going to be on Friday, in which case it wonât be a surprise.â The professor agrees with that and says ok sure it canât be on Friday or else it wouldnât be a surprise, youâre right. But then the same student says âbut for that same reason it canât be on Thursday either, since if itâs Wednesday at the end of class and we havenât had the surprise quiz yet, and we know it canât be on Friday, then we know it must be tomrrow on Thursday. So it wouldnât be a surprise, we could just study Wednesday night.â The professor reluctantly agrees. Then the student repeats this same argument to eliminate Wednesday, Tuesday and Monday as possible dates for a surprise quiz. Confident that there will be no surprise quiz next week after having logically eliminated all possible days in the week, the student goes home and doesnât bother to study. Then on Wednesday next week, the professor begins the class by saying âSurprise! Quiz time.â

So where is the fault in the studentâs logic?

Wikipedia seems more liberal in itâs use of the term

It even lists sudoku as a logic puzzle, which is also generally solved by a process of logical elimination.

Good to see my dislike of and refusal to use wikipedia validated once again. Thanks.

There are logical inferences involved. Rules 4 and 12 are straightforward âcell X is Yâ, but itâs a logical inference from rule 11 and 12 that the oil painter isnât Canadian.. There are more complicated inferences down the line, patterns like âattribute A is either X or Z, but attribute B is either R or S, and if A is X, B canât be either R or S, so A must be Z.â

I agree yours is a logic puzzle, and that itâs a puzzle of a different kind. Iâd call FJâs puzzle one of âapplied logicâ, itâs a logic puzzle in the same way that âsolve for xâ is a math problem. I donât know what to call yours, maybe one of âlogical analysisâ? Youâre looking at someone elseâs applied logic and figuring out where it went wrong.

Good point about Sudoku though, I like those things. I can see how one might refer to them as logic puzzles. Process of elimination and all that. Ok, Iâll concede that it is the case that for any puzzle being solely processes of elimination if those processes of elimination are sufficiently many in number and sufficiently complex then we can reasonably refer to that puzzle as a logic puzzle.

Iâd think in order to maintain some relevant differentiation and meaning to the definition here, we need to factor in the difficulty of the processes of elimination. Otherwise we would be forced to call âBen goes to the store to buy a banana or an apple. He doesnât buy an apple. What does he buy?â as a logic puzzle.

I guess technically it is, just a very very simple logic puzzle. Maybe one you would give to a small child who actually needs to think about it for a second.

Ok, you win. I concede that your original post here is a logic puzzle. Well played sir.

I think this puzzle is a little more challenging than youâre giving credit for. You can really only simply deduce about 6 spaces on the grid before you have to start applying some trial and error, or making a guess and hoping your guess stays consistent with the clues.

True, more difficult sudoku involve making educated or random guesses and testing them out to see if they work or not. That is a process of elimination of eliminating guesses until one of them works. Then you use simple process of elimination on the 1-9 in that row or column you can directly deduce. But Iâm not sure that âmaking guessesâ itself can be considered logical or a part of logic. Hypothesis testing is very important in many cases but would seem to be something other than logic, for example empiricism or brute force trial and error. Kinda the opposite of logic.

Oh it absolutely can. Itâs not uncommon at all to see a proof where theyâre not sure whatâs true, so they assume one thing is true, prove that that leads to a contradiction, and thus determine that that assumption cannot be true. Thatâs the process here too. Itâs parallel to how they prove that square root of 2 is an irrational number.

Itâs a proof by contradiction, and itâs a very important technique in logic and rhetoric.

Proof by contradiction yes. But trial and error brute force, thatâs something different.

If I donât know which of 5 doors has the prize behind it, but there are clues and various meanings about the doors I could work on logically deciphering to try and figure it out, but instead I just start opening random doors until I find the prizeâŚ thatâs more like abandoning logic, not using it.

Itâs logic in the sense that âifâ and âthenâ is used as in formal logic. It is logic to deduce that IF the guy in door 1 likes classical music, AND the guy that has grey hair is next to the guy that likes classIcal music, THEN the guy in door 2 has grey hair. That is a logical deduction that door 2 has grey hair, which is not stated in the clues.

I donât think theyâre mutually exclusive - try something, see if it produces a contradiction, if it does youâve proven that the thing you tried canât be true. Thatâs simultaneously trial by error and proof by contradiction, no?

By that we could say that a dog is using logic when it is digging up the ground looking for a bone it buried before but canât quite remember where the bone is. âIs it hereâŚ nope, is it over hereâŚ nope, is it over thereâŚ oh yeah here it isâ.

Is that really applying logic? I guess you could say the logic applied is something like, âwithin a given spatial grid, it is likely there is a bone buried somewhere in here. I will randomly choose areas to dig up until I find the bone.â That sort of process is unconsciously at work in the dog, just like if you have a dog in the car with you and you turn around a corner the dog will unconsciously shift its body in the opposite direction of the force caused by the turn, to maintain a stable center of gravity and not tip over. The dog doesnât KNOW or UNDERSTAND that itâs doing that, it just does it by instinct and feeling.

For me thatâs the difference. Logic should or does require conscious understanding and knowledge, at least that is what I mean when I think about what is logic. To say that we do things logically and unconsciously would be instead to say that logical processes have been encoded within us at the biological levels and we act these out without realizing it. Yes those things themselves are logical, but it would be incorrect to say that we are doing logic or applying logic when we do them. Like with the dog, it would be correct to say âthe biology of the dog has been structured in such a way as to cause the dog, when it feels motion in one direction, to automatically try to shift its body in the opposite direction a commensurate amountâ and we can call that biological underlying process involved a logical one, but it would be incorrect to say âthe dog is using logic to shift its body to prevent falling overâ.

I will distinguish between logic in-built as structural or unconscious aspects of systems, versus logic used or applied consciously with intent and understanding. Both of these things are referred to by using the same word, âlogicâ. Maybe they are both the same thing and one is simply consciously realized while the other isnât.

Anyway, let me know when you think youâve solved the Surprise Quiz problem.

âIs itâ and ânopeâ are not part of formal logic, âifâ and âthenâ are.

The dog gets to actually try - whereas, in logic puzzles like sudoku or the above, youâre only hypothetically trying. Youâre testing out the option mentally, logically, not submitting your try as an actual answer.

If I said âyou only get one guess at the answerâ, then you can still go away from the thread and do the process of trial and error without actually submitting your tries.

Whereas if I tell the dog you only get one try, and he digs one hole, well if heâs wrong then game over. He canât leave the grounds and mentally try out different digs before submitting his final answer.

Seems like a pretty big difference to me.

Thatâs not really the point I was making though. Whether you or the dog are actually testing out the possibilities in reality physically, or doing them in the mental headspace of imagination, doesnât really change what weâre talking about as to whether or in what instances should we consider such testing/trial and error to be either âexamples of logic itself albeit as rote unconscious biological structuringâ or âusing/applying logic with conscious intent and understandingâ.

It seems like the hugest difference to me. You can logically, mentally do trial and error for this logic puzzle. The dog cannot logically, mentally do trial and error for his bone. Thereâs no logic for him to apply, the bone could be anywhere. But in the puzzle above, the answers canât be anywhere, because some possibilities are logically impossible.