Fact Check: 2 plus 2 equals 4

10) must contend with two questionable consequences of their views: (1) Although the Earth and the Sun were around long before humans and other animals were, the fact that two plus two equals four was not.

In establishing the mundane reality ... 2 + 2 = 4, in De Neutralibus et Mediis Libellus (1652) Johann Wigand said: "That twice two are four; a man may not lawfully make a doubt of it, because that manner of knowledge is grauen [graven] into mannes [man's] nature." In the comedy-of-manners play Dom Juan, or The Feast with the Statue (1665), by Molière, the libertine protagonist, Dom Juan, is asked in what values he believes, and answers that he believes "two plus two equals ...

The identity 2 + 2 = 4 is frequently used for that discussion precisely because it is noncontroversial in all human cultures that have counting numbers and arithmetic up to 4. Which is pretty well all cultures today.

In capitalist schools, we are taught that two plus two always equals four. But Marxism, and science in general, points to a different, more dynamic result, one that more accurately reflects reality. The difference can help us better assess economic statistics and the world as a whole.

Description: Two plus two equals four. For more information, see "2+2=4 Trivia" on the Metamath Proof Explorer Home Page: mmset.html#trivia. This proof is simple, but it depends on many other proof steps because 2 and 4 are complex numbers and thus it depends on our construction of complex numbers.

Finally, there are two important successor-axioms we need to know to prove 2 + 2 = 4: A1: ∀x(x + 0) = x A2: ∀x∀y(x + sy) = s(x + y) So the proof that 2 + 2 = 4 is the following: ... (ss0 + ss0) = ssss0 by Transitive Equality on 5 and 7 ...

Mathematics is part of Stack Overflow’s open communities: specialist spaces where curiosity is welcome, knowledge is shared freely, and the best answers rise to the top. Find your community ... Before you might chastise this quesion, I understand that we all know $2+2=4$. But a while ago I just stumbled across this paper which formally proves that $2+2=4$: http://www.cs.yale.edu/homes/as2446/224.pdf

And if you claim otherwise that can understandably upset some people. For example, the mathematician Kareem Carr recently got fire on twitter for pointing out that 2+2 isn’t always equal four.

To paraphrase: You might say that ... constitutes the more universal unit is a socially constructed decision, and thus 2+2=4 is not universally true because sometimes it’s 2+2 (two and two) = 2+2 (two and two)....