It is very popular for secular people to attempt to base morality on consent. That is, anything is moral to which all relevant parties have consented, and immoral if they haven’t.

Obviously there are a bunch of caveats to both, in the form of cases where consent must be violated for the good of the person (e.g. children, the elderly, etc), and cases where the people are deemed unable to consent (e.g. children, drunks, etc). These do give the lie to the idea that morality is based upon consent since there can’t be exceptions to the foundation of a principle. Obviously these exceptions tell of a deeper foundation for morality which is some conception of the good of a human being which is independent of the human being’s wishes. But if we set this insurmountable objection to the side for the moment, there is a further problem with basing morality on consent: no one can actually give consent.

In modern cant what I mean is that no one can give informed consent, but informed consent is a redundancy. Consent which is not informed is not consent. This is because consent, as a verb, is a transitive verb. I.e. it takes a direct object. You cannot consent in a vacuum. You must consent to something. But in order to consent to it, you must know what it is. It doesn’t mean anything to consent to something, you know not what. What is the content of the consent?

There are generally two ways to try to get around this: the partially correct way and the completely dishonest way.

The completely dishonest way is to arbitrarily terminate the consequences of an action at what is foreseeable. This is attractive to the intellectually lazy, but it makes as much sense as saying that a person can consent to another sawing off the tree branch upon which the first is sitting, but that consent doesn’t extend to the subsequent falling down because they didn’t realize that would happen. The cases where this happens are of course less obvious than this one, but no different in principle.

The partially correct way is to say that a person can consent to classes of action which have some discernible characteristic. Thus for example a person who is having sex in order to produce a child is consenting to becoming a parent, even though they have no idea what sort of child they will receive. The problem is that this depends on the ability to know the outline of the class of action being consented to. And this comes back to the fundamental problem with consequentialism—only God can be a consequentialist.

There are only two ways to know the outlines to a class of action:

1. To be omniscient
2. To receive summary information from someone who is omniscient

Being finite beings, option @1 is closed to us, so the only possible way to achieve consent is option #2. Option #2 is, however, closed to the secular people who are trying to base morality upon consent.

This is, in short, the problem with basing morality upon consent. The only people who might possibly want to, can’t. Those who can, have no reason to try.