In hopes of getting this question off the Unanswered Questions queue, I offer this discussion of the example sentence,
I love not man the less, but Nature more.
The statement in the example sentence can arise only in a situation where the speaker's love has undergone a change. But has the speaker's love remained at a constant level overall, with the amounts devoted to its various component subcategories altered, or has the total quantity of the speaker's love increased, with the allocations to all or some of the component subcategories increased as a result? That's what we need to determine from the speaker's statement.
For ease of description, let's call the speaker's love for man M, the speaker's love for Nature N, and the speaker's total love T; and for simplicity, let's suppose that the totality of the speaker's love consists entirely of the combined amounts of those two component subcategories—man and Nature. Then we can describe the speaker's total quantity of love before things changed as T1, the speaker's love for man at that time as M1, and the speaker's love for Nature at that time as N1. That gives us this simple equation for the person's total love in the earlier time period:
T1 = M1 + N1
More recently, however, things have changed. And what we want to know is, how have the values of T, M, and N changed? We know that T2, M2, and N2 will still look like this:
T2 = M2 + N2
but we don't know which of those values has changed. One possibility is that the total amount of love has remained constant:
T1 = T2
but changes in M and N have occurred, increasing one at the expense of the other. That possibility appears to be the one that the speaker in the example sentence is denying. According to the speaker, the speaker's love of man is not less than it was previously, which means that it is either the same as before or greater than before:
M1 ≤ M2
but at the same time the speaker's love for Nature has definitely increased:
N1 < N2
From these two relations it necessarily follows that the speaker's total amount of love has increased, as well:
T1 < T2
since increasing N while either holding M constant or increasing it by some indeterminate amount must yield a larger T than before.
Transforming these notions back into words, we see that the construction "I love not man the less, but Nature more" can be rephrased as
I love man at least as much as I did in the past, but I love Nature more than I did in the past.