How do formal logicians respond to Marxist/Leninist/Dialectical logic claims? For example, in "An Introduction to the Logic of Marxism", George Novack explains that the law of identity of formal logic, that "A is equal to A", is always falsified when we try to apply it to reality. Here is a quote from the book, in which he quotes from "In Defense of Marxism" (it is long, I apologize): "... a pound of sugar is equal to itself. Neither is this true -- all bodies change uninterruptedly in size, weight, color, etc. They are never equal to themselves. A sophist will respond that a pound of sugar is equal to itself at 'any given moment.' "Aside from the extremely dubious practical value of this 'axiom,' it does not withstand theoretical criticism either. How should we really conceive the word 'moment'? If it is an infinitesimal interval of time, then a pound of sugar is subjected during the course of that 'moment' to inevitable changes. Or is the 'moment' a purely mathematical abstraction, that is, a...

I once took a graduate course in education in which I was the only non-teacher. One day, I disagreed with something said by another student, and her response has always baffled me. She said: "Who are you? You can't question me until you've walked in my shoes." In other words, she felt that I was unqualified to question her, to cast doubt on anything she said. Who was I to say? Well of course her response was nonsense but how so? As a matter of logic or illogic, was her remark an example of an appeal to authority? She certainly felt that she was an authority.

I am having trouble understanding the difference between a 'necessary' and a 'sufficient' condition (in philosophical usage). Would I be right in thinking that the former is a condition that must be present in order for something to happen, while the latter is merely 'enough', i.e. that no other condition needs to be met (while with a necessary condition others can be met)?

A friend once had me consider this logic. Because the Catholic Immaculate Conception doctrine is a cornerstone tenet of the church, but is essentially a dogmatic belief, any dogmatic doctrine canonized by the church must also be as worthy of faith as the Immaculate Conception doctrine. However the doctrine of transfiguration is also a dogmatic belief. Yet even after a priest has blessed the sacramental wine and bread, in reality it does not literally transfigure into the blood and body of Christ even though the doctrine of transfiguration states that it does. If the wine does not literally turn to blood, the doctrine of transfiguration is wrong and because the doctrine of transfiguration is equally as valid as the Immaculate Conception, it too is also wrong by association. However, if the Christ were literally made of bread and wine, then all conflicts would be resolved. Can you please comment on this logic? Thank you

What flaws should one be wary of in an argument? Please explain in layman terms (I have not studied philosophy). Thanks.

As a beginner in philosophy, I got the impression that philosophy is all about arguments. You put in statements (premises), use some rules of argumentation to manipulate these premises, and reach other statements (conclusions). Is there a way to argue for the rules of argumentation themselves? I mean, we use them all the time but how do we know that they are true? What kind of rules would we use to prove the rules of argumentation? Can we use the same rules? Thanks.

If God is omnipotent then surely he can do anything!? My intuition tells me he can defy logic because surely he created it. I know philosophers will then ask me if it is possible for God to create a world where it both doesn't rain and rains at the same time. I am then forced to say that of course this doesn't seem possible. But...this leaves me with two questions: (a) Why do philosophers always have to talk about 'possible worlds'!? (b) Surely a world of contradictions only seems implausible to us because we are reasoning from the knowledge and experience we have in this world. We can't conceive of such ideas as not raining and raining at the same time because we are bound by the logic of this world.

What is analogy? I read Wikipedia's article on the subject and I found it a bit vague or something (for my poor brain, at least...). Is analogy the same as metaphor? Is analogical thinking non-scientific? As far as I see it, politicians are always drawing on analogies. Isn't that just rhetoric? I searched your site and I found the word "analogy" several times, but its use never seemed decisive to answer the questions.

According to Descartes' demon hypothesis, would it be possible for the demon to deceive us about the rules of logical inference e.g. could my belief in the law of non-contradiction be caused by the demon?

Is the Liar paradox, stated as "this sentence is false" false? The Liar surely means, "The proposition expressed by this sentence is false", but this implies that there is one and only one proposition contained within the sentence. If this is not the case then the whole statement is false because "The proposition" must pick out exactly one object. The direct proposition expressed is "This sentence is false", yet surely since the predicate "is false" applies to the sentence in question, "This sentence is false" is false is a proposition that is also logically entwined with the sentence. Since the sentence expresses two propositions, and not one, there is no object which corresponds to "The proposition expressed" and so the whole sentence becomes false.