An Introduction to LogicWritten for independent study and suitable for an introductory course in logic, this classic text combines a sound presentation of logic with effective pedagogy and illustrates the role of logic in many areas of humanistic and scientific thought. Cohen and Nagel's elegant integration of the history of philosophy, natural science, and mathematics helps earn this work its distinguished reputation. 
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4.0 out of 5 stars A UNIQUE INTRODUCTION TO LOGIC, November 6, 2009
By Ole Anders (Coquina Beach, FL USA)
This review is from:Corcoran's edition of the CohenNagel classic An Introduction to Logic (Paperback)
This is the only introductory logic book that discusses the 1931 Gödel axiom system. It is also the only introductory logic book that discusses the distinction between argument forms and argument schemes (patterns). There are many other important topics treated here and nowhere else in introductory texts.
A particularly good and comprehensive intro that focuses upon the relations between formal logic, critical thinking, and scientific methodology. Cohen and Nagel are part of the pragmatist tradition that views logic as the "theory of inquiry" (Dewey's phrase). This approach traces its roots back to Aristotle, but has contemporary adherents of such stature as Jaakko Hintikka.
The approach focuses upon formal logic as a tool for organizing information in the ongoing process of inquiry. Deduction does not so much reveal new data as order our ideas and evidence in such a manner that we are able to ask more effective questions.
The purely mathematical issues are still arguably too centered around the syllogism, but such weaknesses are readily compensated with other texts (Patrick Suppes' classic from the '50's "Introduction to Logic" for example). But even here, the authors' introduction and handling of quantifiers takes things beyond the Greek and Medieval limits.
One of the additional aspects of this book that I especially appreciate is the chapter on measurement. From the above mentioned pragmatist perspective, measurement is most assuredly a "logical" issue, since it is deeply invested in issues of inquiry, and the formal properties of measurement are themselves inherently logical/mathematical in character. (On this last, see Krantz, Suppes, Tversky's "Foundations of Measurement", volumes I  III.)
Contents
THE SUBJECT MATTER OF LOGIC  3 
Partial Evidence or Probable Inference  13 
The Use and Application of Logic  21 
The Traditional Analysis of Propositions 30  28 
Compound Simple and General Propositions  44 
THE RELATIONS BETWEEN PROPOSITIONS  52 
The Traditional Square of Opposition  65 
THE CATEGORICAL SYLLOGISM  76 
The Calculus of Propositions  126 
The Function of Axioms  129 
Structural Identity or Isomorphism  137 
The Independence and Consistency of Axioms  143 
PROBABLE INFERENCE  151 
The Mathematics or Calculus of Probability  158 
Interpretations of Probability  164 
SOME PROBLEMS OF LOGIC  173 
The Reduction of Syllogisms  87 
The Sorites  94 
The Alternative Syllogism  100 
GENERALIZED OR MATHEMATICAL LOGIC  110 
Their Function and Value  117 
The Laws of Thought  181 
AppendixExamples of Demonstration  189 
Exercises  200 
Bibliography of Works Cited  221 