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ESCUELA PREPARATORIA OFICIAL No. 68
CICLO ESCOLAR 2014-2015
TURNO VESPERTINO
MATERIALES DE LÓGICA
NOMBRE DEL ALUMNO: __________________________________________________ GRUPO: _________
Ubicación en el Portafolio de evidencias
Campo disciplinar
Asignatura
Materia
Unidad
Tema
Subtema
LECTURA: Olivera Luna, Rubén, What is Logic? en Hardegree, Symbolic Logic: A first Course, Ch. 1, p.
2; Stock, Deductive Logic, Introduction, pp. 1-12; Walker Atkinson, The Art of Logical Thinking or The
Laws of Reasoning, Ch. I, p. 14; México, 2014.
Logic may be defined as the science of reasoning. However, this is not to suggest that logic is an empirical
science like physics, biology, or psychology. Rather, logic is a non-empirical science like mathematics. Anyway,
distinguishing correct reasoning from incorrect reasoning is the task of logic.
Logic is divided into two branches, namely:
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
Inductive
Deductive
Deductive logic may be defined as the science of the formal laws of thought. The laws of thought are the
conditions of correct thinking.
The distinction between form and matter is one which pervades all nature. In every act of thought we may
distinguish two things:
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
The object thought about
The way in which the mind thinks of it
The first is called the Matter; the second the Form of thought. Formal Logic is concerned only with the way in
which the mind thinks, and has nothing to do with the particular objects thought about.
Since the form may be the same, while the matter is different, we may say that formal logic is concerned with the
essential and necessary elements of thought as opposed to such as are accidental and contingent. By
‘contingent’ is meant what holds true in some cases, but not in others.
Hence logic may be declared to be both the science and the art of thinking. It is the art of thinking in the same
sense in which grammar is the art of speaking. Grammar is not in itself the right use of words, but a knowledge
of it enables men to use words correctly. In the same way a knowledge of logic enables men to think correctly, or
at least to avoid incorrect thoughts.
The laws of thought are all reducible to the three following axioms, which are known as The Three Fundamental
Laws of Thought:
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The Law of Identity = whatever is, is; Every A is A.
The Law of Contradiction = nothing can both be and not be; nothing can be A and not A.
The Law of Excluded Middle = Everything must either be or not be; everything is either A or not A.
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Each of these principles is independent and self-evident.
There are three processes of thought:
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Conception
Judgment
Inference or Reasoning
Conception, which is otherwise known as Simple Apprehension, is the act of forming in the mind the idea of
anything, e. g. when we form in the mind the idea of a cup. Judgment may be resolved into putting two ideas
together in the mind, and pronouncing as to their agreement or disagreement, e. g. we have in our minds the
idea of a cup and the idea of a thing made of porcelain, and we combine them in the judgment “this cup is made
of porcelain”. Inference or Reasoning is the passage of the mind from one or more judgments to another, e. g.
from the two judgments ‘whatever is made of porcelain is fragile’ and ‘this cup is made of porcelain’ we infer a
third judgment: “this cup is fragile”.
Corresponding to these three processes there are three products of thought:
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The concept
The judgment
The inference
When the three products of thought are expressed in language, they are called respectively:
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

The term
The proposition
The argument
The concept is the result of comparing attributes. The judgment is the result of comparing concepts. The
inference is the result of comparing judgments. The term is the result of comparing attributes. The proposition is
the result of comparing terms and the argument is the result of comparing propositions.
Jevons says this truth: “To be a good logician is, however, far more valuable than to be a good athlete; because
logic teaches us to reason well, and reasoning gives us knowledge, and knowledge, as Lord Bacon said, is
power”.
The weakest framework with the most logical mind will conquer in the end; because it is easy to foresee the
future, to calculate the result of actions, to avoid mistakes which might be fatal, and to discover the means of
doing things which seemed impossible.