Secular morality is relative.
Therefore, there is no ultimate, absolute, universal right and wrong in secular morality.
Because of this, there is no reason for anyone to follow secular moral rules.
It amazes me how often I hear something like this line of reasoning trotted out as a defeater for secular morality. I have long seen that it’s a completely vacuous argument, but I haven’t been able to articulate the problem with it.
Now I think I have a nice illustration that can demonstrate why it fails.
Consider the concepts of “up” and “down”.
These are obviously very useful concepts. They are important directions when dealing with actions like standing, lifting, dropping, flying, etc. They also serve as anchors for other concepts like “above/below”, “top/bottom”, “upside-down”, and so on.
It is often very important for someone to be able to identify which direction is “up” and which direction is “down”. To pilots, for example, it is regularly a matter of life and death.
But “up” and “down” have a dirty little secret: they are relative. “Up”means “away from the centre of the Earth”.
But no, even this is too geocentric.* If you’re on Mars, “up” is “away from the centre of Mars”. And if you’re in space … well, it becomes muddier. Does an astronaut experiencing microgravity in orbit around the Earth consider “up” to be “away from the Earth”? What about if you were orbiting the Sun away from any planet? What about the Voyager probes, shooting away from the Sun in orbit around nothing (except, perhaps, the galactic core)?
You see, the concept of “up” is relative. Even if you’re just on Earth, “up” is a different physical direction for someone in Ghana than for someone in Siberia.
An obvious and necessary corrolary of this is that there is no ultimate, absolute, universal “up” or “down”.
So far, “up” and “down” are the same as “right” and “wrong” in a moral system with relative underpinnings (such as one that is based on the shared psychological underpinnings of human nature – ie, relative to the species): they work only within the local frame of reference.
So, is the idea of “up” basically meaningless? Does it have no bearing on individuals? Do we have any way of deciding whether one direction is objectively “up” in a given situation?
Of course, the answer is obvious. If I am in Edmonton, Canada, then “up” is (objectively) the direction that points away from the Earth’s centre at Edmonton. If I am in Kumamoto, Japan, then “up” is (objectively) the direction that points away from the Earth’s centre at Kumamoto.
Similarly, for many secular moral systems, even if there is a relative element in them, it is still relative to something concrete. For example, my current inclination is to base my moral reasoning on principles that I think most people would share, such as valuing individual freedom and preventing harm. So, although my moral system is relative to these human values, the reasoning works as long as I’m talking to people in the same location: that is, as long as the people I’m speaking to share these principles.
This is not proof that secular, relativist morality is superior to theistic alternatives. I don’t know if one can prove such a thing about moral systems (except in cases where a moral system is inconsistent with itself, of course – that is a mark against any set of ideas).
But I hope that the “up/down” analogy will help people understand the faults with the most common objection to relative systems of morality.
* It’s also very imprecise. Due to gravitational effects of mountains and other stuff, the gravitational pull at any particular point on the Earth’s surface isn’t necessarily straight toward the Earth’s centre.