1. **State the problem:** Solve for $X$ in the equation $X = X$. 2. **Understand the equation:** The equation $X = X$ means that the variable $X$ is equal to itself. 3. **Analyze the equation:** Since both sides are identical, this equation is true for all values of $X$. 4. **Conclusion:** The solution is all real numbers, meaning $X$ can be any number. Therefore, the solution set is $$\boxed{\text{all real numbers}}.$$