Listing the English words using encyclopaedic alphabetical collation, and placing the codeword for each beneath it:
- 12 V +
- 10 x <
- 15 P +
- 2 m <
- 7 a >
- 4 c >
- 10 x =
- 19 m <
- 0 P +
- 4 N >
- 16 v =
- 2 J =
- 19 N =
- 14 c >
- 0 N <
- 13 n +
I considered the possibility that the encoding used numerals, not numbers (with e.g. 19 being two numerals), but that seemed unlikely.
The terseness of this code suggests to me references to a codebook. That would allow you to select any word which met your apparent condition whereby
• for each line, the constituent number, letter, and other symbol for each word occurs only once.
It would also explain why the T in Thoughts is the only one with uppercase; an anomaly I do not believe was an error.
The fact that the code is formed from three parts also suggests to me that locating the words in the supposed book requires, or permits, three co-ordinates. The fact that the third component of the possible co-ordinates is evidently limited to 4 permutations (<, >, =, and +) gives us a range of variation for the points on at least one axis. The numerical component would be the unlimited axis; the alphabetical component seems to be composed of 52 (26*2, both upper- and lower- case) points.
If these were Page (number), Line (letter), and Word (other symbol), then we would conclude, from these deductions, that each page in this book consists of 52 possible lines, each with 4 possible words. Very few printings meet such a strict format — especially not those which would feature all the words your key provides, — except one: metrical poetry.
However, metrical poetry rarely is written in such a literary structure, as compared to a more phonetic one. Four words to each line, rather than four syllables?
If it were a book, then we could deduce that the pool of words from which those phrases were constructed spanned no more than 20 pages and was not arranged per the conventional collation of the English alphabet.
Ultimately: I cannot conclude my series of inductions and deductions. Perhaps my work already is adequate to “explain the logic used”.
on page 1 (0), at line 40 (N)
world some more words
< > = +
world is 0N<
Of course, there is some uncertainty as to whether the lines on the page are mapped to letters with the uppercase alphabet preceding the lowercase, or vice versa. With my example, the uppercase succeeded the lowercase: N is therefore 26 (a through z) plus 13 (A through to N).
The only way to be certain of that would involve discovering a corresponding codebook and comparing it with the key which you were given.