Here's why:

* White light is a combination of all colors of the visible spectrum. When all colors are present and mixed, they appear as white.

* Objects absorb and reflect light. The color we perceive is the light that's reflected back to our eyes.

* A white object reflects all wavelengths of light. It doesn't absorb any particular color more than others, so it sends back all the colors of the spectrum, resulting in the perception of white.

Let me know if you'd like to know more about how color works!