I [Daniel Dennett] think it is just as obvious that people can gradually become morally responsible during their passage from infancy to adulthood as it is that lineages of reptiles and then therapsids can gradually become a lineage of mammals over the eons. You don’t have to be an absolute mammal to be a mammal, and you don’t have to be absolutely responsible to be responsible, or have absolute free will to have a kind of free will worth wanting. In fact, since absolute free will would be miraculous, there really needs to be a powerful argument to show why anybody would covet such a thing.
Source:
Philosopher Daniel Dennett’s Book Intuition Pumps