All 6 Uses of

positive
in
The Screwtape Letters

They will positively encourage him to think about realities he can't touch and see.†
Chpt 1 *

positively = with certainty

He can be made to take a positive pleasure in the perception that the two sides of his life are inconsistent.†
Chpt 10

Without that the variety of usage within the Church of England might have become a positive hotbed of charity and humility, Your affectionate uncle SCREWTAPE XVII MY DEAR WORMWOOD, The contemptuous way in which you spoke of gluttony as a means of catching souls, in your last letter, only shows your ignorance.†
Chpt 16

Note, once again, the admirable work of our Philological Arm in substituting the negative unselfishness for the Enemy's positive Charity.†
Chpt 26

Definitions:

(1) (positive as in: I'm absolutely positive!)
certain (having no doubt; or used for emphasis)
(2) (positive as in: had a positive effect)
good or beneficial
(3) (positive as in: positive feedback from my boss)
approval or agreement
(4) (positive as in: a positive attitude)
optimistic (expecting or focusing on good things); or agreeable
(5) (positive as in: The test came back positive.)
found a condition or substance to be present
indicating the presence of something being tested for -- especially a disease, condition, or substance
(6) (positive as in: a positive number)
greater than zero (of a number)
(7) (meaning too rare to warrant focus)
meaning too rare to warrant focus:

See a comprehensive dictionary for less common meanings of positive including some in the fields of electricity, physics, chemistry, medicine, philosophy, and grammar. Note that most all senses of positive indicate that something is good or present.