Which of the following words collectively refers to random or disconnected ideas?

The term "desultory" is used to describe something that is marked by a lack of a plan, purpose, or enthusiasm, often resulting in random or disconnected ideas. When discussing thoughts or discussions that seem to jump from one topic to another without a clear connection, "desultory" perfectly captures that sense of inconsistency and aimlessness.

In contrast, "diatribe" refers to a forceful and bitter verbal attack against someone or something, which does not imply randomness in ideas but rather a focused criticism. "Dichotomy" describes a division into two contrasting parts or classifications, indicating a clear distinction rather than a random assortment of ideas. Lastly, "diffident" pertains to a lack of confidence in one's own abilities or worth, which does not relate to the concept of random or disconnected ideas at all.

Thus, "desultory" is the most accurate choice for describing a collection of random or disconnected ideas.