It is remarkable to observe how unstable our actions on behalf of others are. Our innate evolved rescue impulse is often switched off in indifference; our rationalistic sign post grounded in moral principle ("a common humanity," e.g., Kant, Mill) is often just a thought; our habituated virtues can be easily overridden by negative hierarchies that require callousness; good role modeling from parents or mentors can readily be corroded by bad; empathy and compassion can be overcome by destructive emotions. And a love from above, some spiritual source of love ensconced in religious tradition, can just as easily result in demonization of outsiders as it can in the great works of love that we associate with a Ghandi, a Cicely Saunders, or a Jean Vanier.
The most credible source of altruistic motivation is empathy, the other-oriented emotional response elicited by the perceived condition of another. But empathic concern for others could still be rooted in the need to reduce empathy arousal, in a fear of censure, in a desire for reputational gain, and in gratification. But the best current psychological research indicates that while these exist, from the motivational perspective, these are "unintended consequences." Empathy has been shown in many experiments to provide a direct, unmediated, immediate response to the conditions of others (e.g., C. Daniel Batson).