What do you know for sure, and how do you know it?
In my personal opinion, I prefer to say that one plus one equals two is one of the things I am sure of. There are several reasons why I am sure about this knowledge:
1. It belongs to common knowledge. From school to society, more than 99 percent of people generally accept this knowledge and believe that it is true.
2. It gives me a sense of trust because all the math problems I have dealt with are based on this logic, confirming its correctness at a subconscious level.
If I think about this phenomenon from a critical thinking point of view, the idea of one plus one equals two became a common sense in my consciousness for years, and it also points out a fundamental point that I accept this knowledge because I choose to believe it. Moreover, it is also the idea that the public is in agreement with and has chosen to be believed. But this is going to have a certain degree of a discrepancy with another element, the correctness. If the whole world chooses not to believe something, does its correctness go awry? In other words, will something turn to be absolutely true if the world chooses to believe? Could it be said that accepting knowledge means trusting it?
If a reference to other content, such as the specific size of the moon, I cannot guarantee that I know it for sure, because I have no information about the specific knowledge and cannot confirm its correctness. Most of the time, knowledge is acquired through others. Like listening to a teacher or reading a book written by someone else.
AFTER the PEER review:
I strongly agree with the opinion that knowledge can be varied and distinct from a different perspective. As