What is a eudemon?A spirit of light. :-)
If there is one principle from the works of GKC which truly enlightens me on a daily basis, it is his idea of a heresy. To paraphrase, a heresy is one idea taken out of context of all other ideas. Strong supporting examples are found in the Christological heresies of the early centuries, erroneously teaching that Christ was either a mere prophet, or at the other extreme a divine phantasm with no physical body.
These examples may seem like theological esoterica, but the principle extends into all other fields. In football, offenses score touchdowns, but defense wins championships. The most amazing quarterback still needs a strong running game for support. There are innumerable examples of this in military situations. Technology is a definite aid to combat units, but not at the expense of "old fashioned" soldiering skills. Air power is part of what defines a superpower, but it "boots on the ground" which win wars. I am sure that there are examples of this in every field from horse racing to gardening. No one idea in isolation can be the full truth about anything.
Not a day goes by when I do not use this test when I am presented with new information or challenging situations. I always look at the various sides and a key point in my deliberation is asking the question of which side is overemphasizing a certain fact out of context of all others. Whether it be a financial decision, a matter of taste, or making a purchase, I always seem to be looking to find a "heretic." It would seem that by this method an inquisitive mind may quickly become an inquisitional mind. :-) Have a great weekend!