Word to describe "fleeting, wandering and prone to drifting off" of thought

I was wondering if someone could help me find a word based off of my description.

I would like a word that means something along the lines of "fleeting, wandering and prone to drifting off" or something like this.

I'm trying to describe thought in a "Men fear thought" analysis.

Trying to breakdown the line "Men fear though more than ruin" I was trying to assert that thought is _ as it is "fleeting, wandering and prone to drifting off".

If anyone has some insight into a particularly helpful word, or one that seems to fit well, please let me know!

UPDATE:

I would also like for the word to possibly carry a little bit of a negative connotation, so it can be tied into the analysis of "more than ruin".

Also, I think the word should have its emphasis on "prone to drifting off" and also "leading to other kinds of malicious thoughts/things" if you know what I mean.

Solution 1:

I thought of a third possibility that covers the transition part.

Capricious: governed or characterized by caprice : impulsive, unpredictable.

If I think of something better, I obviously have no compunction against adding another answer. :)

Solution 2:

The question changed a little, so I'm changing my answer. :)

Desultory might work, but it might be a bit of a stretch.

Definition of DESULTORY from Merriam-Webster Online Dictionary 1: marked by lack of definite plan, regularity, or purpose 2: not connected with the main subject 3: disappointing in progress, performance, or quality

Solution 3:

How about "elusive"?