In natural world, we see lots of variety. There are millions of types of molecules and another millions of ways they can be arranged (minerals formation). In biology too there are millions of types of organisms. Natural world is full of diversity.
Where do the diversity comes from? I will answer that in this article.
To know means to be able to predict.
In a given situation whats its behavior will be.
If you can (correctly) predict behavior of your subject then you know your subject.
If you cannot (correctly) predict behavior of your subject then you don't know your subject.
Prediction is litmus test of knowledge. Its litmus test means its the only reliable test in existence.
