I think cutting fingernails is OK. I think cutting fingers isn’t. As far as I know there isn’t a verse mandating the cutting of fingernails, nor a verse prohibiting the cutting of fingers. And yet, if there was a cult that refused to cut fingernails we would think it odd at best, and if we came across a cult that insisted on cutting fingers we would call it evil.
The point here is that you can’t do ethics without observation. You cannot do ethics with just Scripture. That is because you cannot say whether this or that is right or wrong if you do not know what this or that is. Are widgets good? I don’t know. It depends on what they are, and I can’t tell you what they are until I’ve had a look.
Which is not to say that Scripture is insignificant or peripheral to observing the world. In the first instance Scripture will tell us a lot of what we will find, and secondly, if by God’s grace we have been redeemed, then we will also have a regenerate heart which is willing to see what there is to be seen (I’m also wondering if Scripture, thirdly, gives us a way of looking, but I’ll leave it as a query for now).
But it is not enough to see the world, it must also be described, described in morally relevant ways. O’Donovan (in ‘Christian Moral Reasoning’ in Dictionary of Christian Ethics & Pastoral Theology) suggests there are two steps to doing ethics. Firstly a reflective or descriptive step, where you describe the world (set of circumstances) in which you need to act, and then secondly deliberative thinking, where you think towards action.
Most bad ethics, and most ethical disagreements derive from poor and differing descriptions of what we see. In other words, often the most difficult task is not knowing what to do per se, but rather describing the circumstances in accurate and morally relevant ways. Let me give one example:
If two unbelievers are living together, and one of them is converted, should the Christian stay in the relationship. The resolution to this question turns on whether or not their relationship was a marriage. That is, even if they have not formally married, does their relationship resemble marriage or not. So the backpacking couple who share life for six months because it is fun and convenient but who have no intention of ongoing commitment because they live at least three hours from each other in the UK are in a very different situation to the couple who have had a child and bought a house together. In the former we would probably advise the young Christian to end the relationship, in the latter not. The point here isn’t so much the specific issue rather just to note the significance of description.
A large part of ethics, then, is to describe the world we see utilizing the morally relevant categories we discern in Scripture. Thus we can approach and describe situations and circumstances not covered or conceived in Scripture.