Ever since he retired from a desk job 15 years ago, my father has transformed himself into a world traveller and unabashed seeker of new experiences.

He has eaten hand-pulled noodles in Guangzhou, gone scuba-diving in Bali and connected with distant relatives in the Swiss Alps.

Partly, it's just a fun retirement project, but it also stems from an honest recognition of the fragility of life and a conscious decision not to take things for granted.

It's easy to see the wisdom in that decision. The frantic pace of modern life can distract us from the fact that we'll die, so that when we finally become aware of death's inevitable approach, we're left with a litany of regrets. Life seems to have passed us by and we wish we had done more than simply watch.

In general, taking things for granted is considered irresponsible, even damaging.

Taking your spouse for granted is a surefire way to make her feel unloved. Taking your income for granted can put you at financial risk if you lose your job. Taking your health for granted can lead you to take poor care of yourself.

But I'm unconvinced that taking things for granted is always so bad. I think there's something distinctively valuable about allowing many aspects of your life - even the very fact of your life - to recede into the background, into an unconscious mental box we might label "presuppositions".

I would go so far as to say that these presuppositions are what enable you to live a life at all.

A simple way to see what I have in mind is to imagine what would happen if you always heeded the advice against taking things for granted, even in everyday situations.

Imagine that you are driving down a road in an unfamiliar town, that you approach an intersection with a green light and that you drive through the intersection without incident. What makes this experience possible is a presupposition: When you see a green light, vehicles on the cross street see a red light.

Imagine what driving would be like if you did not take this for granted. How bizarre, paralysing and inefficient would it be to stop at each new intersection to confirm the truth of this assumption?

Much of our understanding of the world comes in the form of such obvious presuppositions. But they need not concern only small matters; they occur in more important contexts too.

One of the ways I'll feel that I've succeeded as a father, for example, is if it never occurs to my daughter to wonder whether I love her. I want my love to be part of her taken-for-granted background.

A similar thought applies to my relationship with my wife: Part of what makes ours a committed relationship instead of a casual one is what we are permitted to take for granted about each other (love, fidelity and support for each other's projects).

Without some background assumptions - which, to be sure, may need to be renegotiated every so often - it's not clear that what we have could count as a relationship at all.

What about life itself? A recent medical scare helped me to realise how much I value taking even my own existence for granted.

I went to see my doctor for a routine check-up, which resulted in a biopsy of an abnormal patch of skin on my leg. I later received a phone call informing me that it was squamous cell carcinoma.

As it turns out, squamous cell carcinoma - the second most common type of skin cancer - is not that big a deal, especially in my case, since the patch on my skin hadn't penetrated beneath the epidermis. But I didn't know that at the time of the phone call or during the (very long) week between the call and an appointment with a dermatologist.

In short order, I found myself questioning things I had taken for granted: that I would be around to see my daughter graduate from high school, that my wife and I would grow old together, that I would finish the textbook I'm writing.

One of the things I realised during that week was that part of what I was hoping for, in hoping for an optimistic prognosis, was permission to take all that stuff for granted again. The diagnosis had unearthed those presuppositions, bringing them to the surface, making them available for doubt. As a result, I felt disoriented.

I came to realise that being oriented - having one's bearings - requires being located somewhere, and that being located somewhere requires having some ground to stand on. What we take for granted is that ground.

Don't get me wrong. There are times when I appreciate being reminded to seize the day - for example, when I've been preoccupied with work and my daughter interrupts to ask if I can read her a book.

I'm not suggesting that we sacrifice today on the altar of tomorrow. But I want to seize tomorrow, too, and let it be part of what structures who I am today.

NYTIMES

• The writer is an associate professor of philosophy at Western Washington University.