Lately in my philosophical discussions it has occured to our group that one unexpected and seemingly unlogical thing has started happening.

It would seem to me that using logic is unavoidable in a philosophical debate. Is it really so?

Sometimes when trying to prove something I don't use pure logic but rely more on the "feeling" that two examples have something in common which results in concluding that if I agreed on the first thing then it would seem I agree on the second aswell.

i.e. Wouldn't you say that if I like people I should like animals aswell?

What my task for you is could you provide me with an obvious use of logic in making a philosophical deduction.

My question following is if you can not use strict logic in making a philosophical deduction then can you actually make any sure deduction at all? Is philosophy really just the art of persuading?

Before it seemed to me that if you make some shaky axioms then at least you will be able to build up a system over them, but now it seems to me that you can't really deduct anything and it has really left me feeling helpless.

  • About : "not use strict logic in making a philosophical deduction", I think that if we want to make correct deduction - in philosophy or other topics - we have to use logic ... fullstop. The isuue is : why we have to assume that philosophy is only deduction ? At least for some purported "first principle" to be assumed in order to "hang up" our deductions, we have to argument about them, without being able to deduce them. – Mauro ALLEGRANZA Sep 19 '14 at 10:17
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    If I understand what you're asking, I would suggest that you consider philosophizing a two stage process. First, you use associative reasoning, that is your vague understanding of what thoughts are associated with other thoughts to bring them about, to produce arguments. Then you use logic to critique those arguments formally. Logic alone is best thought of as a critic and lacks creative power. Over time, your associative reasoning becomes more and more logical, and that's why philosophers no longer really see it as a two stage process. – Kevin Holmes Sep 19 '14 at 16:07
  • @mauro just because you say something because you are sure of it doesnt make me believe you any more. Thats the whole point of this topic – ditoslav Sep 20 '14 at 17:20
  • @kevin That's what's the problem. Associative reasoning isn't an exact method. Saying two things are the same in a way can always be disputed by nitpicking – ditoslav Sep 20 '14 at 17:24
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    I'm saying you use associative reasoning to clarify the argument, and formal logic to critic the argument. – Kevin Holmes Sep 20 '14 at 19:06
up vote 4 down vote accepted

What would be the relation between logic and philosophy?

To quote Wikipedia:

Logic is the use and study of valid reasoning. The study of logic features most prominently in the subjects of philosophy, mathematics, and computer science.

whereas

Philosophy is the study of general and fundamental problems, such as those connected with reality, existence, knowledge, values, reason, mind, and language. (Wikipedia)

Therefore philosophy is not primarily the art of persuading; rhetoric is:

Rhetoric is the art of discourse, an art that aims to improve the capability of writers or speakers to inform, persuade, or motivate particular audiences in specific situations. (Wikipedia)

As for your example

i.e. Wouldn't you say that if I like people I should like animals as well?

To me that form of argument seems like an analogy which is also a form of logical reasoning whose validity is however not necessary, and therefore doesn't qualify as a definite argument or statement in scientific or philosophical discussions, nevertheless, as we'll see later, it can serve as a compelling subject for logical examination (scientific and/or philosophical).

That's because since in science and (especially in) philosophy we are pursuing definite and certain knowledge about beings, only arguments that are logically necessary and do not entail uncertain implications are recognized as acceptable arguments. And since the strongest form of argument is deduction, they are the primary form of argument in philosophy.

Additionally to ascertain that beyond the formal validity of arguments, their constituent premises (axioms) are also true all statements must be reducible to the most basic and evident truths whose validity is 100 percent certain and definite. These self-evident truths or principles include the law of identity and non-contradiction. See this article for primer discussion. Every other premise beyond them must be ultimately traced back to them via logically valid line of analysis.

But if your axioms have not been directly or indirectly inferred from the first-evident principles, through a logically valid line of reasoning -- where only deduction yields 100 percent certainty -- then it means that you have simply no philosophy. In other words if your axioms are 'shaky' then it means that the entire system of statements inferred from them will be consequently shaky; a house of cards that will partially or entirely collapse once some or all of your premises are negated.

Example of Applied Inductive and Deductive Reasoning

Now as an example of applied deductive and inductive reasoning, let’s take your own argument and see if we can verify it through these modes of reasoning:

We first form a problem: why do humans love animals?

Then form a general hypothesis: Humans love things with which they have something in common.

We prove it through induction: We love our spouses, our siblings, our colleagues, our fellow nationals with all of whom we have something in common.

We form a second hypothesis: Humans have a lot in common with animals too.

We prove it through induction: Animals are animate and have emotions, like us.

Therefore it follows by deduction that: we love animals because they have a lot in common with us.

The deduction as laid out in common pedagogical form:
Humans love things with which they have something in common.
Humans have certain things in common with animals.
Therefore Humans love animals.

However if any of our premises are disputed, our conclusion may be either entirely undermined or only modified. For example if we argue that: Humans do not necessarily love things with which they have something in common under certain circumstances. For example they do not love thieves so long as they want to steal from them. And they do not love predatory animals so long as they want to attack them.

However as you can see the above challenges can at best only limit the implications or conditions of validity of our conclusion which can be easily sorted out by applying slight changes to our premises and conclusion. But at times they can entirely undermine the conclusion. This can be done for our example if one can completely disprove that humans love things with which they have something in common.

  • What bothers me is the necessity of the generalisation of the induction needed to make a deduction. It seems to me that more problems can arise from such statement than can be helped to make a conclusion. If you are trying to argue with someone who disagrees he can say that they are not common in the same way and so the deduction is invalid. What scares me is that you can always find differences between something you are using to deduct via induction and therefore can always dispute the validity of the induction. – ditoslav Sep 19 '14 at 11:22
  • @DominikDitoIvosevic Welcome to the world of induction and uncertainties involved with the method. There's no denial by anyone familiar with the topic that induction is always open to correction as there are seldom perfect inductions. To again quote Wikipedia: "While the conclusion of a deductive argument is supposed to be certain, the truth of the conclusion of an inductive argument is supposed to be probable, based upon the evidence given." And I have already suggested that the conclusion can be refuted if any of the premises are negated. – infatuated Sep 19 '14 at 11:43
  • Thank you for the warm welcome :) I was kinda hoping that I had missed something which helps in making better deductions because the idea of this being the best method leaves bad taste in my mouth – ditoslav Sep 19 '14 at 12:19
  • @DominikDitoIvosevic, well it must be very evident why deduction is the strongest form of argument. There is for example no possibility of errors associated with sensual observation in inductive reasoning. The conclusion solely follows from the premises. However deduction doesn't guarantee truthful conclusions if any of the premises are untrue. Deductive reasoning only guarantees formal validity of the reasoning. That must have been the intuitive reason for the bad taste in your mouth! :) – infatuated Sep 19 '14 at 12:31
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    "... inductions are ampliative. Induction can amplify and generalize our experience, broaden and deepen our empirical knowledge. Deduction on the other hand is explicative. Deduction orders and rearranges our knowledge without adding to its content." SEP, problem of induction – Kevin Holmes Sep 20 '14 at 22:28

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