Front Page Titles (by Subject) Popper & Objective Knowledge - Literature of Liberty, Autumn 1980, vol. 3, No. 3
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Popper & Objective Knowledge - Leonard P. Liggio, Literature of Liberty, Autumn 1980, vol. 3, No. 3 
Literature of Liberty: A Review of Contemporary Liberal Thought was published first by the Cato Institute (1978-1979) and later by the Institute for Humane Studies (1980-1982) under the editorial direction of Leonard P. Liggio.
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Popper & Objective Knowledge
“Karl Popper, Objective Knowledge, and the Third World.” Philosophia 9(December 1979):45–62.
Karl Popper's theory of the “third world” (the world of the imaginable) needs an amendment in order to account for its autonomous and objective character. Popper distinguishes three worlds: (1) the first world is that of physical objects; (2) the second world is that of the mental acts (or dispositions to behavior) that we direct towards physical or mental objects; (3) the third world is those mental objects themselves that form the content of our theories, arguments, books, libraries, etc.
Problems arise when Popper attempts to establish that the third world is both man-created and “objective,” or autonomous. The example of the natural numbers simply does not work, for while the numerals we choose to describe these natural numbers are man-created, the numbers themselves are discovered and are therefore not man-created. Similarly, the numerals that we use to describe natural numbers are as physical as chairs or tables, so we should consider them as elements belonging to “world number one.”
However, sentences and numerals are properly distinguished from meanings and numbers, the modified “third world” could include meanings and numbers as both nonphysical, discovered, and completely autonomous or objective. That would give the following components to our total world:
S: the linguistic form in which a number or theory is formulated;
C: the objective content expressed by S;
M: the mental act or state of X; and
P: (where relevant) the fact in the physical world to which S refers.
Now, the logical relationships and unintended consequences of “C” can be understood as both autonomous and not manmade, forming a bona fide “third world.”