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Introduction to Logical Reasoning

Understanding Logical Reasoning
  • Introduction to Logical Reasoning
  • Developing the Skills
  • Logical Links
  • Sequencing and Arrangement
  • Team Selection
  • Miscellaneous
Human life is full of situations where one is called to make a decision. This also includes making significant choices about what to believe and what not to. Although everyone prefers to believe what is true, we often disagree with each other about a particular issue due to the subjective nature of our judgements. We often find individuals or groups locked in conflict because our reactions to situations are guided by our impulses. Humankind has developed a mechanism through which we are able to move beyond our individualistic and idiosyncratic notions and establish indisputable facts. This mechanism is called Logical Reasoning and Logic has come to play a very important role in ascertaining what is more credible or whose reasoning is sounder.

It is imperative to understand that Logic is not mainly concerned about finding the ‘Truth.’ Logic’s prime interest lies in finding that, which can be established as a fact using several strands of reasoning supported by sophisticated arguments. It may seem like a big coincidence that the event or situation that is correct will have more substantial proofs or arguments in its favour, rather than the even or situation that is not so


Example :
If we are discussing about the direction from which the sun rises, we will always have more proofs or stronger arguments in favour of east rather than west. However, if somehow we get more proofs or stronger reasoning in favour of south, then it is more logical to say that the sun rises from south than to say that it rises from east.

An important application of the logic is in the area of law and the judicial system—an area where proceedings are heavily dependent on logical processes—of any civilized society. The following example tells a lot about the logic and its constituents:

While pronouncing his verdict in one of the most senstational murder cases in India, the judge said, “Though I know that this is the man who committed the crime, I acquit him, giving him the benefit of doubt.”

What is the judge saying?
Even though he knows that the defendant is indeed the culprit, the fact has not been proven, that is, it cannot be logically deduced on the basis of arguments and evidence; consequently the accused has to be acquitted.

Despite the above example some authoritativeness can indeed be attached to the way of logical reasoning. No matter how sceptical we are about the points from where we begin to reason, if we follow the rules of logic we will reach an acceptable conclusion. It is almost always possible to distinguish between correct from incorrect reasoning independent of our agreements or disagreements regarding substantive matters. Logic is the discipline that studies the distinction—both by determining the conditions under which the truth of certain beliefs leads naturally to the truth of some other belief, and by drawing attention to the ways in which we may be led to believe something without the respect for its truth. This provides no guarantee that we will always arrive at the truth, because the beliefs or assumptions with which we begin are sometimes erroneous. But following the principles of correct reasoning does ensure that no additional mistake creeps in during the course of our progress.

Hence, Logic can be seen as a tool using which we find out the strength of reasoning or the various arguments put forward in favour of or against something. This is reflected in the origin of the word ‘logic’. It takes its roots from the Greek work logos which means reason or principle. Taking a broad view, we can see several dimensions, or usages of the term logic. Some of these are given below:
  1. A system of reasoning: Aristotle’s logic.
  2. A mode of reasoning: By that logic, we should sell the company tomorrow.
  3. The formal, guiding principles of a discipline, school, or science.
  4. The relationship between elements and between an element and the whole in a set of objects, individuals, principles, or events: There’s a certain logic to the motion of rush-hour traffic.
  5. In the field of Computer Science the term, logic, may mean any of the following:
    1. The non-arithmetic operations performed by a computer, such as sorting, comparing, and matching, that involve yes-no decisions.
    2. Computer circuitry.
    3. Graphic representation of computer circuitry.

Terms Related to Logic

  1. Consistency—An attribute of a logical system that is so constituted that none of the propositions deducible from the axioms contradict one another.
  2. Completeness—This is an attribute of a logical system that is so constituted that a contradiction arises if any proposition is introduced that cannot be derived from the system.
  3. Corollary—An inference that follows directly from the proof of the another proposition.
  4. Non sequitur—A conclusion that does not follow from the premises.
  5. Subject—The first term of a proposition.
  6. Predicate—What is predicted about the subject of a proposition.
  7. Proof—A formal series of statements given showing that if something is a fact, then something else necessarily follows from it.
  8. Paradox—A self contradiction (As in the statement—‘I always lie’ is a paradox.)
  9. Postulate—A declaration of something self evident.
  10. Proposition—A statement that affirms or denies something and is either true or false.
  11. Negation—A proposition that is true if and only if another proposition is false.
  12. Axiom—A proposition that is always true and does not require proofs or disproofs to be true.
  13. Tautology—A statement that is always necessarily true (As in the statement—‘He is honest or he is not honest.)
  14. Contradiction—Opposite of Consistency.
  15. Logical relation—A relation between propositions.
  16. Inductive Reasoning—Proceedings from particular facts to a general conclusion.
  17. Deductive reasoning—Proceedings from general facts to a particular conclusion.

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