The Online Library of Liberty

A project of Liberty Fund, Inc.

• Introductory Note.
• Book I.
• Chap. I.: Whether a Demonstrative Science Exists
• Chap. II.: What Knowing Is, What Demonstration Is, and of What It Consists
• Chap. III.: A Refutation of the Error Into Which Some Have Fallen Concerning Science and Demonstration
• Chap. IV.: The Meaning of ‘distributive,’ ‘essential,’ ‘universal’
• Chap. V.: From What Causes Mistakes Arise With Regard to the Discovery of the Universal. How They May Be Avoided
• Chap. VI.: Demonstration Is Founded On Necessary and Essential Principles
• Chap. VII.: The Premises and the Conclusion of a Demonstration Must Belong to the Same Genus
• Chap. VIII.: Demonstration Is Concerned Only With What Is Eternal
• Chap. IX.: Demonstration Is Founded Not On General, But On Special and Indemonstrable Principles; Nor Is It Easy to Know Whether One Really Possesses Knowledge Drawn From These Principles
• Chap. X.: The Definition and Division of Principles
• Chap. XI.: On Certain Principles Which Are Common to All Sciences
• Chap. XII.: On Questions, And, In Passing, On the Way In Which Sciences Are Extended
• Chap. XIII.: The Difference Between the Demonstration and Science of a Thing’s Nature and Those of Its Cause
• Chap. XIV.: The Figure Proper to Demonstrate Syllogism
• Chap. XV.: On Immediate Negative Propositions
• Chap. XVI.: On Ignorance Resulting From a Defective Arrangement of Terms In Mediate Propositions
• Chap. XVII.: On Ignorance Resulting From a Defective Arrangement of Terms In Immediate Propositions
• Chap. XVIII.: On Ignorance As Resulting From Defective Sense Perception
• Chap. XIX.: Whether the Principles of Demonstration Are Finite Or Infinite
• Chap. XX.: Middle Terms Are Not Infinite
• Chap. XXI.: In Negations Some Final and Ultimate Point Is Reached Where the Series Must Cease
• Chap. XXII.: In Affirmations Some Final and Ultimate Point Is Reached Where the Series Must Cease
• Chap. XXIII.: Certain Corollaries
• Chap. XXIV.: Whether Universal Or Particular Demonstration Is Superior
• Chap. XXV.: That Affirmative Is Superior to Negative Demonstration
• Chap. XXVI.: Direct Demonstration Is Superior to Reduction Per Impossible
• Chap. XXVII.: What Science Is More Certain and Prior, and What Less Certain and Inferior
• Chap. XXVIII.: What Constitutes One Or Many Sciences
• Chap. XXIX.: Concerning Many Demonstrations of the Same Thing
• Chap. XXX.: On Fortuitous Occurrences
• Chap. XXXI.: Sense Perception Cannot Give Demonstrative Science
• Chap. XXXII.: On the Difference of Principles Corresponding to the Difference of Syllogisms
• Chap. XXXIII.: The Distinction Between Science and Opinion
• Chap. XXXIV.: On Sagacity
• Book II.
• Chap. I.: On the Number and Arrangements of Questions
• Chap. II.: Every Question Is Concerned With the Discovery of a Middle Term
• Chap. III.: The Distinction Between Definition and Demonstration
• Chap. IV.: The Essence of a Thing Cannot Be Attained By Syllogism
• Chap. V.: Knowledge of the Essence Cannot Be Attained By Division
• Chap. VI.: The Essence Cannot Be Proved By the Definition of the Thing Itself Or By That of Its Opposite
• Chap. VII.: Whether the Essence Can In Any Way Be Proved
• Chap. VIII.: How the Essence Can Be Proved
• Chap. IX.: What Essences Can and What Cannot Be Proved
• Chap. X.: The Nature and Forms of Definition
• Chap. XI.: The Kinds of Causes Used In Demonstration
• Chap. XII.: On the Causes of Events Which Exist, Are In Process, Have Happened, Or Will Happen
• Chap. XIII.: On the Search For a Definition
• Chap. XIV.: On the Discovery of Questions For Demonstration
• Chap. XV.: How Far the Same Middle Term Is Employed For Demonstrating Different Questions
• Chap. XVI.: On Inferring the Cause From the Effect
• Chap. XVII.: Whether There Can Be Several Causes of the Same Thing
• Chap. XVIII.: Which Is the Prior Cause, That Which Is Nearer the Particular, Or the More Universal?
• Chap. XIX.: On the Attainment of Primary Principles
• Appendix. Prior Analytics. Book II.
• Chap. XXIII.: On Induction
• XXIV.: On Example

CHAP. I.

On the number and arrangements of Questions

The subjects of enquiry are equal in number to the objects of scientific knowledge. We enquire about four things, the fact of the phenomenon, its cause, whether it exists and what its nature is. Now when we ask whether a thing is this or that, taking two alternatives, e.g. asking whether the sun is eclipsed or not, we ask about the fact. A proof of this is that when we find that it is eclipsed we abandon this line of enquiry. Also if we know from the first that it is eclipsed we do not ask whether it is eclipsed or not. Next, after learning the fact of the phenomenon we seek for the cause of it. For example, when we know that the sun is eclipsed or that the earth does move, we go on to seek for the cause of the eclipse or of the movement.

These questions concerning the fact and cause stand towards each other in the relation here stated, but in some questions the enquiry proceeds differently: namely whether a thing exists at all or not; e.g. as to whether or not a centaur or a god is. By ‘whether it is or not’ I mean is absolutely, not whether a thing is, e.g., white or not white. When we know that the thing does exist we enquire about its nature, asking, for instance, ‘What then is a god, or what is a man?’