An act undertaken with negative intentions is therefore, under deontology, immoral irrespective of its beneficial consequences. The two theories therefore differ in the principles that while utilitarianism is based on consequences of actions, deontology is based on responsibility and motives into actions (Mann and Roberts, 2012. Ahronheim, Moreno and Zuckerman, 2005).
Both deontology and teleology have inherent problems. Teleology undermines justice as it can promote an unlawful practice as long as the practice results in more benefits than harm. It is also difficult to quantify consequences of actions. Deontology is however rigid and may lead to harmful actions. Similarly, deontology’s observance of rules may lead to confusion especially “when values or assumptions conflict” (Mann and Roberts, 2012, p. 16).
Teleological ethics that requires attention to consequences is therefore a problem because it may induce conflict with legal provisions since a beneficial consequence may be achieved through illegal means. This means that the theory undermines justice. Social dynamism also means that long term consequences of present actions on future actions cannot be predicted, a matter that further undermines utilitarianism (Mann and Roberts, 2012,