1. Ethical Theories
High-level account of how questions about morality should be addressed.
Similar to engineering models?
V=IR: a tool to solve many engineering problems. V=IR is not a law of nature; neither is F=ma: think about scale
Ethical theories also do not describe the world – only some good answers to moral dilemmas 
Ethical problems are not clear and people and society are unpredictable and messy
Many ethical theories to choose from

2. Some traditional ethical theories
Consequentialist:
Evaluate acts, policies and institutions according to consequences.
Right action is the one that has the best consequences 
Utilitarianism: Only happiness is good in itself. Everything else is
a means to happiness. (pain, suffering == - happiness)
An act is right if it tends to increase the sum of human
happiness; wrong if reverse.
(Or RULE utilitarianism … )
Most decision-making strategies and models originate with utilitarianism: cost-benefit analysis, game theory, risk-benefit analysis 
What is the chief problem these theories face?
Various forms: ethical egotism, nationalism, (altruism? – really maximizes total happiness? Gift of the Magi (O. Henry))

3. Other traditional ethical theories
Deontological theories
 Certain actions are right or wrong regardless of consequences
Immanuel Kant: Follow universal principles that require respect for persons – absolute value of persons.
Categorical Imperative: (for example, truth telling)
Act only according to that maxim that you could at the same time will to become a universal law
Kant formulated DUTY ethics – saying how persons have the DUTY to act
Another deontological theory:
Theory of rights (of persons). E.g. right to life, right of choice. John Locke: natural rights – life, liberty, property. We exchange our natural state of anarchy for the liberty and security of the society – social contract.

4. Kant’s Perfect and Imperfect Duties
When violating a “maxim” would, under the Categorical Imperative (first form):
lead to a logical contradiction (if universalized), we have a “perfect duty” not to violate the maxim (example – universalizing stealing  meaninglessness of “property”)
lead to an undesirable condition (if universalized), we have an “imperfect duty” not to violate the maxim (example – universalizing not helping others except for one’s own good  wouldn’t ever want to ask anyone for help one couldn’t then repay, so we SHOULD help others without regard for our own repayment, when possible)

5. A Second Form of Kant’s Categorical Imperative
"Act in such a way that you treat humanity, whether in your own person or in the person of any other, always at the same time as an end and never simply as a means"
-- Kant, Immanuel; trans. Ellington, J.W. [1785] (1993), p.36

6. KCI – Third Formulation
"Therefore, every rational being must so act as if he were through his maxim always a legislating member in the universal kingdom of ends."
Ibid., p. 43