Grant’s Razor: the only thing that truly matters in life are your relationships

Dave Cortright
3 min readNov 9, 2022


The Harvard Study on Adult Development has been going on for nearly 100 years. It started following 268 Harvard University male graduates from the classes of 1939–1944 throughout their entire lives in parallel with 456 men who grew up in low-socioeconomic Boston households. The study has tracked their major life events, their lifestyles, and their medical histories. All of that data from all of those people across all of those years boiled down to one simple truth:

“Good relationships keep us happier and healthier. Period.”

A previous study director, George Valliant, puts it even more bluntly:

“The only thing that really matters in life are your relationships.”*

I call this Grant’s Razor:

The only thing that truly matters in life are your relationships: with others, but also with yourself.

The William T. Grant Foundation is the original funder of this study, and they absolutely deserve credit for being a visionary supporter of this effort.

Philosophical razors are very useful tools in eliminating large swaths of possibilities as irrelevant. Common misbeliefs about the impact of achievement, wealth, fame, diet, and exercise are completely obliterated by Grant’s Razor. For example, The Roseto Effect shows that strong communal relationships outweigh poor diet. Even disease can be no match for relationships. Our social genes so much want us to have strong connections with others, that they will quite literally step up and save our lives (ᴘᴅꜰ) when we commit ourselves to healthy social connections. Even The Blue Zones (which are essentially “longevity communities”) all have a strong community as a foundation. That more than makes up for the fact that one of the nine lifestyle habits in Blue Zones is regularly ingesting a known Group 1 carcinogen (alcohol).

Grant’s Razor goes hand-in-hand with The Bowlby Conjecture. The only things you need for a long, healthy happy life were all available to our ancestors 50,000 years ago on the African savannah. And chief among them are the strong social bonds that kept the tribe together. As Johann Hari said in his insightful book, Lost Connections:

“Every human instinct is honed not for life on your own, but for life… in a tribe. Humans need tribes as much as bees need a hive.”

Robin Dunbar goes even further in his excellent treatise Friends:

“Social measures most influence your chances of surviving… The best predictors [of survival] are those that contrasted high versus low frequencies of social support and those that measured how well-integrated you are into your social network and your local community. Scoring high on these increases your chances of surviving by as much as 50%…

It is not too much of an exaggeration to say that you can eat as much as you like, drink as much alcohol as you want, slob about as much as you fancy, fail to do your exercises, and live in as polluted an atmosphere as you can find, and you will barely notice the difference… You will certainly do yourself a favor by eating better, getting more exercise, and [taking your meds], but you’ll do considerably better just by having some friends.

So given this information, how can we use it to improve the world? I have an idea that combines the concept of “4ᴀᴍ friends” from the Grant Study and “moias” from the Blue Zones into Peer Support Groups (PSGs).

* George Valliant’s actual quote is “The only thing that really matters in life are your relationships to other people.” But this is imprecise. Firstly, it really should be with other people, because truly healthy intimate relationships are bidirectional, not one way. Secondly, the relationships we have with other sentient creatures (such as our pets or animals in nature) matter equally as well. Thirdly, I would expand this to include the relationship one has with oneself. Our frugal brains use the same neural pathways for all relationships. It’s imperative to have a good relationship with oneself in order to have good relationships with others. So the more precise modified quote I prefer is “The only thing that truly matters in life are your relationships: with others, but also with yourself.”

On the name: my apologies to the Gluecks. I absolutely recognize you have done amazing things in service of this discovery. But Grant-Glueck is simply unwieldy.

Friends in close relationships

Also see The Bowlby Conjecture.



Dave Cortright

Professional coach, effective altruist and audaciously optimistic about helping to fix the global mental health crisis.