  Second, Elliot Sober and David Wilson argue that evolutionary theory supports altruism.  Parental care might be explained on egoistic grounds: a belief about the child’s distress causes the parent pain that the parent believes she can alleviate by helping, or the parent believes that she will be caused pain if she does not help.  Parental care might also be explained on altruistic grounds: the parent has a non-instrumental desire that the child do well.  Lastly, parental care might be explained by a combination of these mechanisms.  Sober and Wilson argue that more reliable care would be provided by the altruistic or combination mechanisms.  Given the importance of parental care, this is a reason for thinking that natural selection would have favoured one of these mechanisms.  The egoistic mechanism is less reliable for several reasons: beliefs about the child’s distress may fail to cause the parent pain (even bodily injury does not always cause pain, so pain is unlikely to be always caused by beliefs about distress); the parent may fail to believe that helping will best reduce her pain; there may not be enough pain produced; the combination view has the advantage of an extra mechanism.