LOGIC

Logic is the formal systematic study of the principles of valid inference and correct reasoning.It refers to the methods and principles used in distinguishing correct from incorrect reasoning.Logic examines general forms which arguments may take, which forms are valid, and which are fallacies.In philosophy, the study of logic is applied in most major areas: ontology, epistemology, ethics, metaphysics.Logic is the science of correct reasoning .It is not a description of how people reason or it will be reduced to sociology or psychology . Logic is concerned with possible arguments whether people know them or not.Logic is concerned only with Validation of arguments that is judging whether a given argument is valid or not.

There are four types of logic

1.Informal logic  is the study of natural language arguments.It is logical to say some things and illogical to say others .For example ''from the money in my pocket you can not infer what I will buy ,because we may not trade only with money ,but also with consumption goods like fish and chicken .Words like love,remembering and person have logical powers that is fixed relationship with the meaning of other words .for example love is a feeling not because it can be put to test like toothache.Informal is the mapping of such relations , a grammar of what can be said sensibly.Informal logic is the whole of the rules governing the use of such content laden words .The study of fallacies is an especially important branch of informal logic. The dialogues of  Plato[6] are good  examples of informal logic.

2.Formal logic is the study of inference with purely formal content. An inference possesses a purely formal content if it can be expressed as a particular  application of a wholly abstract rule, that is, a rule that is not about any particular thing or property. The works of Aristotle contain the earliest known  formal study of logic. Modern formal logic follows and expands on Aristotle. In many definitions of logic, logical inference and inference with purely  formal content are the same. This does not render the notion of informal logic vacuous, because no formal logic captures all of the nuance of natural language.It is based on the application of such words and terms as ''and'',''or'',''if'',''then'',''not'',''all'',''some''.

3.Symbolic logic is the study of symbolic abstractions that capture the formal features of logical inference.[8][9] Symbolic logic is often divided into two branches: propositional logic and predicate logic.

4.Mathematical logic is an extension of symbolic logic into other areas, in particular to the study of model theory, proof theory, set theory, and recursion  theory.

Uses of logic

1.Logic helps to secure and implant consistency in speaking and writing.To argue inconsistently means to argue from contradictory positions.

2.Logic helps not only to bring order to thought but to speech and writing in order to gain clarity ,precision and firmness.The lack of logic in theses areas often results in vagueness,feebleness, tautology and wooliness of expression.

3.Since logic tends to correct inaccuracies in speech and writing , it drills the mind towards the attainment of precision,clarity and adds force to arguments.

4.Logic leads to the unity and continuity of education,to the approaches of culture,the definition ,redefinition and refinement of public debate and to the cultivation of human gentility in in both sexes .It is for this reason that logic transcends ordinary grammar and common sense ,reaches the inner recesses of the natural,physical and biological sciences and emerges in philosophy that is knowledge itself.