Kantian Ethics: a different approach
Kantian ethics is perhaps the hardest to grasp. Partly this is due to language: talking about the a priori synthetic or the categorical imperative presents us with a conceptual fog before we even start.
But I'm not sure the essence of Kant is so hard to grasp. Nor do I believe that many of the objections to Kantian ethics really stand up. So let's try to reduce Kant to his raw elements before we apply his thinking to the issue of abortion.
The two great influences on Kant were Jean Jacques Rousseau and Isaac Newton. Rousseau inspired Kant to pursue the idea of the autonomous rational agent free from the impositions of the Church, free to choose the moral way by virtue of the exercise of pure reason, and able to universalise his judgements. Rousseau gave us the idea of the social contract, Kant, the idea of the legislature of moral beings existing in a kingdom of ends and coming up (impartially so to speak) with some idea of the common good and universal rights that guarantee this summum bonum.6
Newtonian science was something that applied, Kant thought, to the phenomenal world or world of matter and time and space. Newton gave us immutable laws such as the law of gravity which came to him as a result of an apple landing on his head. The world of Newtonian physics was a world of the a posteriori because laws come out of experience: the apple hits the head and always will do. It is also contingent because it depends on the natural world being as it is. On the moon, for example, gravity does not work the same way, and there are no trees recycling carbon dioxide, so if we visit the moon , as a contingent fact, I need to wear a space suit, breathe an oxygen cylinder, and I will find myself able to beat the long jump world record (a contingent record) by about three hundred yards.
If all this applied to the Newtonian phenomenal world, could it not also apply to the world of values? Could there not also be a realm of pure reason which was derived a priori not from experience or desire, but simply by the application of reason willing what was good? And the good? The good was definable by applying the categorical imperative which gave us our concept of a right action, one which we ought to do.
Note that a little assumption has been slipped in here, namely that we will what is good, rather than what is evil. Is this argument not circular, in the sense that we assume that we will the good, which leads us to apply the categorical imperative, which then leads us to do the good?
Not exactly. Kant was attempting to objectify morality, to take it away from our subjective desires or selfish interests. He saw clearly, and rightly, that the natural law tradition had used sanctions to try and force us to act in a way that is contrary to our desires, by using fear and punishment. Natural law theory had imposed a conscience on us, but surely there were grounds for arguing that human beings, free from the chains of guilt and fear, could work out for themselves the difference between right and wrong?
This was Kant's great insight: if we simply act on hypothetical imperatives, we act only from our desires. So we say "if I want to stay dry, I will need an umbrella or a lift from Auntie Maud". Note that I don't really need the "if" here. I can just say "I want to stay dry, so I'll take an umbrella". The point is this, it becomes a hypothetical statement because my moral compass is set as it were by my known desires. A hypothetical is also advisory, and so a weaker form of command, whereas a categorical is obligatory - a stronger unconditional "ought".
But isn't there another way to set the compass, a fixed point like the north pole which can give me straight guidance wherever I am and whatever I am faced with? After all, my desires are fluctuating and may be inconsistent or purely selfish.