One of the key principles of money is ‘opportunity cost.’ It means that when I buy something, I have to give up something else in return. We think we buy because we need something, but we often forget that we could buy something else instead. We rarely consider ‘opportunity cost’ when making a purchase. We do not compare other values against our needs. Buying something means giving up something else, but we often don’t realize it. When we spend money, we should also consider the ‘opportunity cost’; yet, in reality, we aren’t trained to do so. By making a purchase, we bypass the value comparison that may not offer any additional benefits. Maybe it’s because we lack knowledge, or perhaps the idea isn’t appealing. - Joseph’s “just my thoughts”
"Apples are the fruit" is a true proposition. At this time, "apples" are a Sufficient Condition to be fruit, and vice versa, because the "fruit to be an apple is more necessary for other conditions such as "red, round", the fruit is a Necessary Condition to become an apple. If the proposition of "If you respect someone, you'll get married" is "true," it's a "Sufficient Condition" to find someone you admire for marriage, but it's just only a "Necessary Condition" to find someone to marry for respect. Even with respect, you can not get married. You can't get married even if the Reverse Proposition is "true." Because marriage is a matter of "choice" before conditions or needs. If you want a respectable man, you can find a great man. To live comfortably, you can find a rich man. So, is there no Necessary-Sufficient Proposition for a marriage (conditions where both the proposition ...