Let’s say you had the chance to become a vampire. With one magical bite you would gain immortality, superhuman strength and a life of glamorous intensity. Your friends who have undergone the transformation say the experience is incredible. They drink animal blood, not human blood, and say everything about their new existence provides them with fun, companionship and meaning.  Would you do it? Would you consent to receive the life-altering bite, even knowing that once changed you could never go back?  The difficulty of the choice is that you’d have to use your human self and preferences to try to guess whether you’d enjoy having a vampire self and preferences. Becoming a vampire is transformational. You would literally become a different self. How can you possibly know what it would feel like to be this different version of you or whether you would like it?  In her book “Transformative Experience,” L. A. Paul, a philosophy professor at the University of North Carolina at Chapel Hill, says life is filled with decisions that are a bit like this. Life is filled with forks in the road in which you end up changing who you are and what you want.  People who have a child suddenly become different. Joining the military is another transformational experience. So are marrying, changing careers, immigrating, switching religions.  In each of these cases the current you is trying to make an important decision, without having the chance to know what it will feel like to be the future you.  Paul’s point is that we’re fundamentally ignorant about many of the biggest choices of our lives and that it’s not possible to make purely rational decisions. “You shouldn’t fool yourself,” she writes. “You have no idea what you are getting into.”  The decision to have a child is the purest version of this choice. On average, people who have a child suffer a loss of reported well-being. They’re more exhausted and report lower life satisfaction. And yet few parents can imagine going back and being their old pre-parental selves. Parents are like self-fulfilled vampires. Their rich new lives would have seemed incomprehensible to their old childless selves.  So how do you make transformational decisions? You have to ask the right questions, Paul argues. Don’t ask, Will I like parenting? You can’t know. Instead, acknowledge that you, like all people, are born with an intense desire to know. Ask, Do I have a profound desire to discover what it would be like to be this new me, to experience this new mode of living?  As she puts it, “The best response to this situation is to choose based on whether we want to discover who we’ll become.”  Live life as a series of revelations.  Personally, I think Paul’s description of the problem is ingenious but her solution is incomplete. Would you really trust yourself to raise and nurture a child simply on the basis of self-revelation? Curiosity is too thin, relativistic and ephemeral.  I’d say to really make these decisions well you need to step outside the modern conception of ourselves as cognitive creatures who are most sophisticated when we rely on rationality.  The most reliable decision-making guides are more “primitive.” We’re historical creatures. We have inherited certain life scripts from evolution and culture, and there’s often a lot of wisdom in following those life scripts. We’re social creatures. Often we undertake big transformational challenges not because it fulfills our desires, but because it is good for our kind.  We’re mystical creatures. Often when people make a transformational choice they feel it less as a choice and more as a calling. They feel there was something that destined them to be with this spouse or in that vocation.  Most important, we’re moral creatures. When faced with a transformational choice the weakest question may be, What do I desire? Our desires change all the time. The strongest questions may be: Which path will make me a better person? Will joining the military give me more courage? Will becoming a parent make me more capable of selfless love?  Our moral intuitions are more durable than our desires, based on a universal standard of right and wrong. The person who shoots for virtue will more reliably be happy with her new self, and will at least have a nice quality to help her cope with whatever comes.  Which brings us to the core social point. These days we think of a lot of decisions as if they were shopping choices. When we’re shopping for something, we act as autonomous creatures who are looking for the product that will produce the most pleasure or utility. But choosing to have a child or selecting a spouse, faith or life course is not like that. It’s probably safer to ask “What do I admire?” than “What do I want?”  A version of this op-ed appears in print on August 25, 2015, on page A19 of the New York edition with the headline: The Big Decisions. Today's Paper|Subscribe
The most important decisions in life should be based not on what we think we want, but on what or whom we admire.