- The earth is flat, “FE”;
- The earth is a sphere, “SE”;
- The earth is an oblate spheroid, “OE”. (An oblate spheroid is a sphere that “bulges” at the equator. It is a “squashed” ball; a tangerine rather than an orange).
“A description D approximately fits a state S (i.e, D is approximately true of S) if there is another state S’ such that S and S’ are linked by specific conditions of approximation, and D fits S’ (D is true of S’).”
(Psillos, 1999, p. 277)
“Let x and y be two terms having the relation P. Then there are to be two terms z, w, such that x has the relation S to w, y has the relation S to w, and z has the relation Q to w.”
(Russell, 1920, p. 54)