Explanation | Details | Example |
---|---|---|

1. Conceptual Understanding | The numbers “2” and “4” represent quantities, and “+” means combining them. By definition, “2 + 2” results in “4.” | Two objects + two objects = four objects |

2. Formal Systems (Logic) | In formal arithmetic (Peano axioms), “2 + 2 = 4” follows logically from the rules and definitions of numbers and addition. | Symbolic: 2 + 2 = 4 (within arithmetic) |

3. Empirical Experience | Based on real-world observation, adding two objects to two more results in four objects, reinforcing the concept. | 2 apples + 2 apples = 4 apples |

4. Innate Cognitive Structures | Research suggests that humans may be born with an intuitive understanding of small quantities and basic arithmetic, making simple operations like “2 + 2 = 4” natural. | Infants can distinguish between 2 and 4 |

The statement “2 + 2 = 4” is something we know based on several factors: logical consistency, definitions, and cognitive processes. Here’s how we come to know this:

### 1. **Conceptual Understanding (Definitions)**

- The number “2” represents a quantity of two objects, and the operation “+” refers to combining quantities.
- “4” is defined as the quantity you get when you combine two pairs of objects. So, by definition, “2 + 2 = 4” because the concept of “4” includes two sets of two.

### 2. **Formal Systems (Mathematical Logic)**

- In mathematics, this is established through axioms, which are foundational rules accepted without proof. In the standard arithmetic system (Peano arithmetic), the statement “2 + 2 = 4” follows from these basic axioms.
- We use symbols like “2,” “+,” and “=” according to strict logical rules. Based on these rules, “2 + 2 = 4” is a tautology — a truth by virtue of the system’s structure.

### 3. **Empirical Experience (Cognitive and Practical Observation)**

- From a young age, we observe objects and learn counting. If you have two apples and then add two more apples, you can observe that you now have four apples.
- This basic experience reinforces our abstract understanding of addition. While mathematics doesn’t rely on physical objects for its truth, these experiences help us intuitively grasp concepts like addition.

### 4. **Innate Cognitive Structures**

- Some cognitive scientists argue that humans may be “hardwired” to understand basic mathematical concepts like counting and addition. There’s evidence that even infants and some animals have a basic sense of numbers and quantities, suggesting an innate grasp of simple arithmetic.

In summary, we know that “2 + 2 = 4” because it’s a logical truth built on definitions and formal rules, reinforced by our practical experience with quantities in the world. It’s an example of how abstract reasoning and empirical observation come together to support mathematical knowledge.