(Wow, two posts at one time: it's kinda scary.)
Many years ago, a Greek philosopher named Eubulides of Miletus posed what has since come to be known as the Sorites (or Heap) Paradox. It goes something like this:
"One grain of sand is not a heap. So if you have one grain of sand, you do not have a heap. Now, if you add one grain of sand (which is not a heap) to something that is not a heap (your original one grain), it is still not a heap. You now have two grains of sand, which is not a heap. Add one more grain of sand (3 total), and it is still not a heap. Add another grain of sand. And another. And another. Even when you have 10,000 grains of sand, you do not have a heap. It follows that there are no heaps."
It can work in reverse, too:
"Suppose you have a heap of sand [assume 10,000 grains]. If you remove one grain of sand, you still have a heap. If you remove one more grain, you still have a heap. So one grain of sand is not a heap and does not affect whether something is or is not a heap. Continue removing grains, and you eventually have a heap of sand made up of zero (0) grains."
A modern version might look like this:
"(1) If a person has only $1,
quem is not rich.
(2) One dollar less or more does not affect whether or not a person is rich.
(3) Thus, a person with $100 is not rich, nor is a person with $100,000, nor a person with $100,000,000,000,000,000, nor anyone else, for that matter: no one is rich."
And the paradox can apply to other things, as well: baldness, fullness, tallness, knowledge, etc.
There are several resolutions of the paradox:
(1) The "ideal language" proposition, which asserts that terms like "heap" and "rich" are too vague to be valid objects for logical reasoning.
(2) The "epistemic" theory, which says that terms like "heap" and "rich" contain specific "cut-off lines" that govern when the terms apply. The problem is that we can never know exactly where those cut-off lines are.
(3) The "many-valued" or "fuzzy" logic standard, which dictates that a statement can have more than two truth values (classical logic says that a statement is either "true" or "false"); thus, there are
degrees of baldness, heapness, knowledge, etc.
It's interesting to think about the places you see this puzzle in life, used both ways. "Why should I vote; my one little vote won't make any difference." "Why should I help with Project X? One more person won't make any difference." "Donate money, even if it's only $1. Every little bit counts."
It's scary to think that every action we take, no matter how small, could have dire consequences somewhere down the line. At least, it's scary until we remember Romans 8:28 and other hope-giving passages. Then it's just creepy.