Doubt is crucial. There is no change without doubt. There is no possibility without doubt. There is no evolution without doubt. There is no dynamism without doubt. There is no realisation without doubt. There is no vision without doubt. Doubt is a crucial driving force both within and without of the individual.
Certainty is in the domain of belief. Certainty creates a narrowness of vision and destroys context. Certainty is the driving force of specificity and limits the ability to see something as it really is or limits the ability to see possibilites. Certainty restricts the ability to see the whole or as much of the whole as it is possible to see.
Doubt over certainty is closely linked to questions and answers as posited before. Doubt leads to questions and questions are life. Certainty is based on answers and answers are death.
Belief can be substituted for certainty exactly as above. Doubt is central to confusionism and doubt does not carry the negative contotations ascribed to it in common parlance. Doubt indeed is precisely the opposite and a driving force for recognising the human condition and finding a way in a culture stymied by the control of a society trained and coerced on belief, certainty and an unachievable push to know all.
To doubt is to start to understand and recognize. To doubt is to start to find a way in the modern world that will be less confusing and frustrating than a way based on pure belief or certainty.