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The three kinds of inference that Peirce would come to refer to as ''abductive'', ''deductive'', and ''inductive'' inference he gives his earliest systematic treatment in two series of lectures on the logic of science: the [[Harvard University]] Lectures of 1865 and the [[Lowell Institute]] Lectures of 1866. There he sums up the characters of the three kinds of reasoning in the following terms:
The three kinds of inference that Peirce would come to refer to as ''abductive'', ''deductive'', and ''inductive'' inference he gives his earliest systematic treatment in two series of lectures on the logic of science: the [[Harvard University]] Lectures of 1865 and the [[Lowell Institute]] Lectures of 1866. There he sums up the characters of the three kinds of reasoning in the following terms:
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<p>We have then three different kinds of inference:</p>
<p> Deduction or inference ''[[a priori and a posteriori (philosophy)|à priori]]'',</p>
<p> Induction or inference ''[[à particularis]]'', and</p>
<p> Hypothesis or inference ''[[à posteriori]]''.</p>
<p>(Peirce, "On the Logic of Science" (1865), CE 1, 267).</p>
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Early in the first series of lectures Peirce gives a very revealing illustration of how he then thinks of the natures, operations, and relationships of this trio of inference types:
Early in the first series of lectures Peirce gives a very revealing illustration of how he then thinks of the natures, operations, and relationships of this trio of inference types:
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<p> If I reason that certain conduct is wise
<br>because it has a character which belongs
<br>''only'' to wise things, I reason ''à priori''.</p>
<p> If I think it is wise because it once turned out
<br>to be wise, that is, if I infer that it is wise on
<br>this occasion because it was wise on that occasion,
<br>I reason inductively [''à particularis''].</p>
<p> But if I think it is wise because a wise man does it,
<br>I then make the pure hypothesis that he does it
<br>because he is wise, and I reason ''à posteriori''.</p>
<p>(Peirce, "On the Logic of Science" (1865), CE 1, 180).</p>
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We may begin the analysis of Peirce's example by making the following assignments of letters to the qualitative attributes mentioned in it:
We may begin the analysis of Peirce's example by making the following assignments of letters to the qualitative attributes mentioned in it: