On what ground may the philosopher combat the universal opinion, the dictum of common sense and of science?
When we look into his reasonings, we find that he is influenced by the error discussed at length in the last section--he has confused the phenomena of the two orders of experience.
I have said that, when we concern ourselves with the objective order, we abstract or should abstract, from the relations which things bear to our senses.

We account for phenomena by referring to other phenomena which we have reason to accept as their physical conditions or causes.
We do not consider that a physical cause is effective only while we perceive it.

When we come back to this notion of our perceiving a thing or not perceiving it, we have left the objective order and passed over to the subjective.

We have left the consideration of "things" and have turned to sensations.
There is no reason why we should do this.

The physical order is an independent order, as we have seen.