Ven Dhammanando:
It's true that there is an implicit distinction in the Suttas
between (1) unwholesome doubt (e.g., scepticism regarding the
qualities of the Triple Gem), (2) commendable doubt (e.g., when one
doubts doubtworthy claims, as in the opening to the Kālāma Sutta),
and (3) ethically indifferent doubt (e.g., wondering whether one
should go left or right to get to Rājagaha).
However, these distinctions need to be determined contextually.
They have nothing to do with which word for doubt the Buddha
happens to use. In the Suttas the various words for doubt (kaṅkhā,
vicikicchā, vimati, saṃsaya etc.), along with the verbs from which
they derive, are all used synonymously and
interchangeably.
Best wishes,
Dhammanando Bhikkhu
One further remark:
What I wrote in my last post concerns Sutta usage. In the
Abhidhamma, however, vicikicchā is never wholesome or neutral, but
is always an unwholesome mental factor. The question sometimes
arises as to how to reconcile the abhidhammic claim that vicikicchā
is always bad with those sutta passages in which this seems not to
be the case. One does so as follows:
1. When vicikicchā is being commended in the Suttas, it is to be
understood as referring to the mental factor of understanding
(paññā), with the Buddha using the word 'vicikicchā' merely to
conform to common worldly usage.
2. Ethically indifferent doubt, such as wondering how to get to
Rājagaha when one arrives at a crossroad, is referred to as a
"counterfeit of a hindrance". Abhidhammically this is described not
in terms of the presence of the mental factor of vicikicchā, but
rather, in terms of the absence of the mental factor of decision
(adhimokkha).
Best wishes,
Dhammanando Bhikkhu