It might be indifferent to pleasure, pain, mutilation, and death. That which is judged to be good or bad would be motivationally inert to it. Though it is possible in principle for there to be sentient beings whose beliefs and desires are not guided by reason, there is a biological advantage in having beliefs and desires guided by reason. Evolution has a role in explaining how there came to be human beings having brains which endow them with a degree of intelligence. So evolution has a role in explaining why human beings tend to have reason for believing what they believe and for desiring what they desire.
Intelligence has survival value.
It is the nature of an object's being good that when we are aware of good properties in good types of objects, there is, under certain circumstances, reason for us to seek and choose objects of those types. A component of a person's intelligence is a disposition to form desires for objects when he is aware of qualities in those objects which there is reason to desire. Thus, the tendency people have to desire and pursue good objects when we are acquainted with good properties of those objects is contingent on some fact about the nature of people. Thus there are two parts to the explanation of why people want and seek pleasure and other goods. First, it is the nature of an object's being good that the object has a property which, when people are aware of it, provides them, in certain circumstances, reason to desire, seek and choose that object.