It is easier to find words for ideas than for forces because:

Explanation

The passage says many of the forces are covertly included within the ideas, so the ideas come to words more readily.

Note: Passage II (from William Empson, Seven Types of Ambiguity, 1930) is copyrighted and is not reproduced. Its argument: logical connectives are often unnecessary or misleading; the 'forces' that hold a poem's ideas together are mostly carried inside the ideas, so ideas are easier to name than forces; forces and ambiguity are complementary, so forces cannot be discussed simply as ambiguity; where a poem holds a contradiction, the tension must be conveyed and sustained.