Clyde Rathbone says his website Letter will help make the world a better place

He, along with brother Dayne and business partner Monish Parajuli have created a platform called Letter for people to have long-form conversations, discuss topics and ideas, and ,most importantly, learn from each other.

They believe thoughtful conversation is what's missing in the online world, where more people are spending more time.

"We believe very strongly in the power of conversation," Mr Rathbone said.

"Nothing substantial has ever been achieved without [effective communication and collaboration]. Civil discourse is fundamental to human progress."

Letter aims to harness the best bits of Facebook and Twitter, without the unintended consequences of the technology, like the increased idolisation and echo chambers.

Mr Rathbone truly believes it will make the world a better place, and his arguments are convincing.

He uses the analogy of two people sitting in a cafe, deeply engaged in a conversation when a random person who has overheard the discussion intervenes, rejects whatever is being said and then disappears.

That is what it was like on social media, Mr Rathbone said. But he doesn't want to be too critical of Facebook or Twitter.

"The technology itself is mindblowing. The fact you can communicate with anyone from anywhere, it's just huge and we take it for granted," he said.

But Letter will harness the best bits of those platforms and cut out the negatives. It will work exactly as the name suggests. One person writes another person a letter.

The initial letter-writer can invite someone specific to participate in that conversation, or they can throw it out to the world for anyone to respond (that's a new feature, it's called Letter in a bottle). The catch is, the conversation can only be between two people. Anyone could see the letters, and that was part of the beauty, Mr Rathbone said. He hopes others can learn from the respectful, thoughtful conversations.

The team members believe so deeply in the product they have lived on very little for the past five years, learning hard lessons along the road. The first iteration of their idea, the first version of Karma, was shelved after it was panned by psychologists and cyber bullying experts as being a website that promised to be "like Yelp or TripAdvisor for humans".

Karma version two is a place to express gratitude to people, but it's on the backburner as the team focuses on Letter.

The hard work looks to have paid off. Letter has made it to the final round of the biggest, most successful start-up "incubator". Y-Combinator has helped companies like Airbnb and Dropbox scale to a wider audience to become successful platforms. If the interview on December 5 is successful, Letter could be the next big thing.

"It's terrifying and exciting. There's a lot riding on it, every time I think about it I start sweating," Mr Rathbone said.

What they need now - and what they believe the world needs - is more people writing letters.

"We need people who believe in the power of conversation," Mr Rathbone said.

"We have conversations on Letter about very niche, esoteric subject matters that don't have widespread appeal but the people who care about it, they really care about it. Then we have conversations about things like parenting, schooling, health and wellbeing.

"If you're a thoughtful person and you feel like conversation is important and you like learning by having dialogue, then come to Letter. That's who we need."

He's written about religion, parenting (he's dad to 18-month-old Hugo), free speech, belonging... his next letter will be about meditation.

"I'm a failed meditator. I would like to write a letter about the struggle and pose the question for people who have successfully mastered it how they did that," he said.