You might want to read Schopenhauer who argues four points as well. You know I am dutch, so the words I use may not be the proper translation. Who knows my dabbling can get you anywhere.

The fourfold root of the law of sufficent cause.

Knowing causality is the only function of the intellect according to Schopenhauer. The first, always present aspect of the intellect is the observation of the phenomena. This is causal in all ways and thereby all perceptions are intellectual. Because of this the intellect is not seperate from percieving, nor of determining the relations. This is the basis for experiencing.

'The world is my imagination'

The four grounds: