Very few people in the travel, tourism and hospitality industry have not felt the impact of Philip Wolf and what he created at Phocuswright.
There are those who knew him personally, such as his family, friends and colleagues - many of the latter being people he nurtured and inspired as he built the business into the research and events powerhouse that it is today.
And then there are those in the industry that he interviewed on-stage, when conducting research or eventually working alongside in the numerous company boards of directors that he joined after retiring from an executive role at Phocuswright in 2011.
Finally, there are the many that his work and ideas touched indirectly, probably without even realizing it. They perhaps, most likely, do not even know his name.
That's what leaders and visionaries are able to do.
His death this week after a short illness has led to an outpouring of moving and fascinating tributes from every corner of the industry.
They are moving because his passing is a huge shock to so many (he was interviewing travel CEOs for the ITB trade show just last week) and fascinating because they indicate just how influential he was.
There are a string of pivotal moments in his career that many will point to, such as the creation of a world-class conference that connected, inspired and often wowed those who attended.
Or how he assembled a pack of extraordinarily smart analysts who understood how to slice and dice the travel industry to produce industry-defining research.
But perhaps his lasting legacy comes in his passion to shine a spotlight on the burgeoning online travel sector in the late-1990s and then position it - through the conferences and research - as the continued driving force for change in the wider travel, tourism and hospitality industry.
As well as leading the charge of the digital travel economy from its nascent days to being part of the mainstream, he was able to listen, reflect and establish new ways of thinking about how it might develop.
Arguably the best example came in 2006, just as online travel had settled pretty comfortably into its position in the market.
Rather than rest on its laurels, he asked whether the sector was ready to "confront the establishment" amid the explosive development of Web 2.0 - and, thus, Travel 2.0 was born.
The principles around that term (personalization, social travel, real-time and dynamic pricing and engagement, looking beyond the browser, next-gen distribution, etc.) were put forward during one of his famous conference monologues.
His ability to communicate these elements and, more importantly, argue why such a monumental next step in the development of online travel was coming whether people liked it or not, laid the basis for discussions, ideas and launches (both products and startups) for years to follow.
There are countless startups, for example, who will recall how he would often listen to their ideas, ponder for a moment, before sharing an experience or a tip that he genuinely hoped would help them out.
Despite a reputation as a fearsome and unrelenting interviewer (this is a good thing), he was fair and also cunning in knowing how to play both the crowd and the interviewee to produce some memorable moments over the decades.
But behind that sometimes tough exterior, ultimately he had a very simple mission: to share knowledge and ideas and take the industry along for the ride with him. It's difficult to locate a trend or idea that he identified - or Phocuswright produced - that did not come to fruition.
What so many of this week's tributes have noted, alongside the influence on the industry, is his warmth of spirit and generosity.
Although Philip took himself and the professionalism of the company and what it did incredibly seriously, he invariably did so with a mischevous grin on his face and always with a story to tell.
Many will recall how - always with a cheeky glint in his eye - he would often remark something along the lines of "I'm going to bring this little bit of information up when I interview them later" as he prepared to face down another company CEO at the conference.
And then, later, both would be laughing backstage or at a cocktail party, more often than not with his wonderful wife Carol Hutzelman, who built the company alongside him. He was able to do that and be respected for it.
For those who found themselves invited to his home in Sherman, Connecticut, or later on Massachusetts' Cape Cod, he could entertain, evangelize about a new idea, recall minute details of information or simply watch and smile to himself as those around would joke, argue or come up with the next big or crazy plan.
The Phocuswright family is a very sad one this week.
But we all know that Philip would not want us to mourn for too long - there is plenty of buzz to keep palpable, to modify one of the well-known phrases that is so often associated with his time at Phocuswright.
RIP.