"Easier" is an adjective.  The word "easier", in particular, is almost never used as an adverb. Colloquially, you could say something like, "It'll go easier if you do it this way." But if you try to use "easier" as a universal substitute for "more easily", you end up sounding uneducated. You need to use the adverb, "more easily":

> In order for us **more easily** to perceive that non-humans have agency, ...

or

> In order for us to **more easily** perceive that non-humans have agency, ...

The addition of "that" is not absolutely necessary but makes the sentence flow better.  Without it, the reader's first impulse is to assume that "non-humans" is the object of "perceive".  That this is not the case becomes clear pretty quickly, but the addition of "that" ensures that the confusion does not occur in the first place.