All 4 Uses of

subjective
in
The Screwtape Letters

Once all his thoughts and images have been flung aside or, if retained, retained with a full recognition of their merely subjective nature, and the man trusts himself to the completely real, external, invisible Presence, there with him in the room and never knowable by him as he is known by it—why, then it is that the incalculable may occur.†
Chpt 4 *

subjective = influenced by personal belief, feelings, or preferences (rather than being based purely upon fact)

The general rule which we have now pretty well established among them is that in all experiences which can make them happier or better only the physical facts are "Real" while the spiritual elements are "subjective"; in all experiences which can discourage or corrupt them the spiritual elements are the main reality and to ignore them is to be an escapist.†
Chpt 30

Thus in birth the blood and pain are "real", the rejoicing a mere subjective point of view; in death, the terror and ugliness reveal what death "really means".†
Chpt 30

The hatefulness of a hated person is "real"—in hatred you see men as they are, you are disillusioned; but the loveliness of a loved person is merely a subjective haze concealing a "real" core of sexual appetite or economic association.†
Chpt 30

Definitions:

(1) (subjective)
influenced by personal belief, feelings, or preferences (rather than being based purely upon fact)

Subjective is often contrasted to objective--meaning based upon fact without the influence of personal feelings or preferences.
(2) (meaning too rare to warrant focus)
meaning too rare to warrant focus:

In grammar, subjective can refer to a noun or pronoun inflection that indicates the relationship between terms in a sentence. For example, in "She ran home," she is the subject of the verb ran and the sentence is in the subjective (aka nominative) case.