Ly Tin Wheedle
Ly Tin Wheedle is referred to as arguably the Disc's greatest philosopher in a number of the books - however, it is generally him that's doing the arguing! As he lived sometime in the distant, forgotten past, he does not actually appear as a character in any Discworld novels; rather his pithy statements are quoted in many different contexts.
The first mention of Ly Tin Wheedle is in the opening pages of The Light Fantastic (where his name is spelled "Weedle"): "... it is said that someone at a party once asked the famous philosopher Ly Tin Weedle 'Why are you here?' and the reply took three years."
Created the Singing Spoon. His many sayings advocating respect for the old and the virtues of poverty are frequently quoted by the rich and elderly. Some of his aphorisms are below:
"The only thing known to go faster than ordinary light is monarchy", according to the philosopher Ly Tin Wheedle. He reasoned like this: "you can't have more than one king, and tradition demands that there is no gap between kings, so when a king dies the succession must therefore pass to the heir instantaneously. Presumably", he said, "there must be some elementary particles -- kingons, or possibly queeons -- that do the job, but of course succession sometimes fails if, in mid-flight, they strike an anti-particle, or republicon." His ambitious plans to use his discovery to send messages, involving the careful torturing of a small king in order to modulate the signal, were never fully expounded because, at that point, the bar closed.
"Chaos is found in greatest abundance wherever order is being sought. It always defeats order, because it is better organized."
When the philosophical community came to the conclusion that distance was an illusion and all places were in fact the same place, Ly Tin Wheedle was the philosopher to make the famed conclusion that "Although all places were in fact the same place, that place was very big".
The author of this annotation was travelling with the real-life inspiration for Gytha Ogg back in the mid-1980's. The latter was recounting with great delight an alcohol-fuelled conversation in one of the bars at a science fiction convention around that time, at which TP was present, where the subject of instantaneous communication based on the transfer of kingship was discussed. Apparently, the consecration of ground was another property that was considered to be instantaneously conferred, at whatever distance. Vampires, of course, are repulsed by holy ground. So the idea was floated of a piece of land being sequentially consecrated and un-consecrated by a remote bishop, over which was dangled a vampire on a spring balance. The story reports that TP "suddenly went very quiet and thoughtful".
While the conversation about kingons and queons did in fact make it into print (albeit in a footnote), the concept of the "vampire on a spring balance" disappointingly seems to have failed so to do.