触れる challenges my concept of what を does; to mark a direct object.
Consider these uses of 触れる:
（人）の頬に指を触れる (Touch a finger to someone's cheek)
（人）の頬に手を触れる (Touch someone's cheek with your hand)
Now, if transitivity of the verb were not taken into account, I would guess that it's the finger or hand that is being touched since they are marked by the direct object marker
を. But because I know that
触れる is intransitive, I understand that the object is marked by
(Question) What is the role of
を when used in the above type of pattern? Should the particle be
で instead since
手 are the "means" by which the action was carried out?