What Paul says about having children seems to me to ring equally true of marriage. Until you have spent a lifetime in the company of another person, you can't possibly know what it's like to do so. When we get married, there is an important sense in which we really don't know what we're doing. This doesn't make marriage a complete leap into the dark, of course you can be pretty sure that another person is well-suited to you, that you have similar goals, that you love each other, and so on. Even so, no matter how much you know about another person on the day of your marriage, you still don't really know what yourte doing in marrying them. This doesn't make you wrong or irrational to do it anyway; it's just part of what it is to be human. Living as a finite being means projecting oneself toward the unknown.