How do you know if a product that doesn't exist yet doesn't exist for a good reason?

"I have something nobody has ever done before!"

Humans have created black holes, built robots with hive intelligence, and perfected the self-cooking TV dinner. You could absolutely have something that hasn't been done and I'm not challenging that. Make sure you temper your excitement against reality, or you'll risk myopia.

Determining why something doesn't exist, unless you're writing your doctoral dissertation on a larger topic and ruling out alternatives, is a waste of time. You need to determine if the problem you believe exists does exist, and then you need to determine how best to solve it (as opposed to building something that you and you alone believe is the solution).

"Go pitch everyone on your idea!"

No.

"Find the users and pitch them on your idea!"

Still no.

"If you build it, they will come!"

Not quite the line from the movie, but no.

"Pitch a lot of folks on your solution!"

No again.

"Find the users and pitch them on your solution!"

Aaand no.

Find specific people who you think have this problem and... "ASK ABOUT THE PROBLEM?!?!?!"

No. Not yet, anyway.

Ask them what their top 3 challenges are. Do not ask, "What are your top 3 challenges with (problem)?" Ask, "What are your top 3 challenges?" If the problem you're looking to solve comes up in that top 3 list, tell them it is interesting they have (problem), and then ask non-leading questions about that problem, such as:

"What do you find most frustrating about (problem)?"
(keep digging into this one, you need to get to the absolute root pain point)

"What is it you do today to try and work through or around the problem?"

"Are there any tools you use to help with (problem)?"
(also known as "how to find your competition")

"What does the perfect solution to (problem) look like to you?"
-"Why that solution?"
(keep digging into this again and you'll get to the absolute root solution for that person)

"How much does that problem cost you today (in revenues, or new customers, or customer retention... ask all of the above and more)?"

"What are you spending to address the problem?"
-"It doesn't sound like you're getting your money's worth. What else do you need to get out of your current solutions (which you should know after all of those other questions) in order to get real value out of them and solve this problem either once-and-for-all or on an ongoing basis?"

See what you're doing? You aren't pitching. You aren't telling them, "I'm going to fix it this way and I hope you like it." You're identifying their real challenges, what those pains cost them, what their current tools are and how they're failing, how they want the problem solved, and what they're willing to pay.

Now do this again, and again, and again. Log all the answers and find commonality. You need to get to X potential customers, meaning "people with the same problem, each looking for the same solution, and each willing to pay Y". When X*Y is enough to cover your initial costs, then you can go solve the problem.

Whether you ultimately want to solve the problem at that point or not - given the solution may be radically different than what you thought it would be, or X would be too numerous to manage, or Y is so low OR high (perhaps prohibitively-so to their employer(s), and so on - well, only you can answer that question once you get there.

Assuming you do "get there"!

Does your product satisfy a particular need? Did you have to overcome obstacles that required unique insights/technology to get there?

Make sure you really understand what needs are, or what "jobs to be done" are, and you'll be able to tell a good product idea from a bad one more easily.

The book When Coffee and Kale Compete is a good resource on that topic.

Take the scientific approach to validate.

Define a hypothesis about what problem your product solves and for who. Then, go out and find those people and pitch them and see if it resonates.

You'll either prove your hypothesis or disprove it. Most likely, you will learn new insights about the problem and the customer.

Then rinse and repeat until you get to product-market fit =)

that's a trick question, because some entrepreneurs could have tried and failed to promote a product just because they tried in a bad way.

You need to know if potentials customers (not users, customers) exist and how much you could charge, at least to launch a viable product. That's the main questions imo.

There have been a lot of helpful comments already so I'll just add this, I know it doesn't answer your question but make sure you're not falling for this trap. The image is from this article btw.

Try to look at this not from the product perspective. Instead, look what's "behind" your product. What problem does it solve? Why would people need/want this?

Next, find out what people are currently using to fill that need/want. If that need/want is truly present, there will be something out there that's currently filling that void, that's virtually a guarantee.

This could provide you with a number of different insights:

1. People simply don't need/want this product
2. You find out your products does indeed exists, perhaps in a slightly different form
3. People are using something completely different to fill that void; something you would not have envisioned

This is a spectre.
On one end, you have all the typical lean startup advice: build small rapid prototypes, learn from failure, get feedback. The further you go in that direction, the safer it gets - you'll practically never work on something that nobody needs.
On the other end, there's the more creative and artistic approach: you like building stuff, you may or may not have a need for it, and can't know how or if people will respond. The risk that you might be wasting your time trying to cash it in is huge. The pleasure of doing something exactly how you like it is incredible though.
The biggest trouble with the lean method is that very few of today's giant companies were built that way. Did Zuckerberg ask people if they want a social networking site, or did he just started working on it? Did the Google brothers do market research and gather feedback on whether people need a new search engine, or did they just started working on a phd? That's why the risk is huge - beause the reward is huge as well.

to put it as simple as possible.. I think you really need to figure out is there a gap in the market...and a market in the gap. If so, why? What is the actual problem you are solving and who are you solving it for? Then ask yourself, why are you trying to solve it (the purpose behind your drive) and how are you solving it (do people engage with your UX)?

Pieter Levels says "validate by launching" 🚀

YMMV

I would talk to prospects before you execute. Many times there is a need. Is the need great enough for people to pay for it? If so, how much? Depending on the players in the industry and the product, it may not have value, it may have value or the value is not enough for major players to worry about.

Going from zero to one is hard (cf. Pieter Thiel’s book), specially for bootstrapped startups, I’d add.

I’d also argue that you are better off having some competitors.

Past failed startups could have failed for multiple reasons, so focus on active competitors.

The real test, as already mentioned, is talking to people. Are they willing to pay for your product?

Sales is the silver bullet.

You talk to people who you think would buy it... OR you talk to people who you think should have built it by now and ask them why they haven't.

This is going to depend a lot on the niche you're working in.

Is the product something you yourself needed? How did you come up with the idea for this product? What does this product do?

Talking to potential customers should be a priority throughout the entire lifecycle of your product.

I'd try ship a closed beta as soon as possible to validate the idea.

There's only one way to tackle this - ask people!
Ask co workers, attend meetups and ask people, email people who have potentially tried something like that and ask them what went wrong.
Next, create and spreadsheet and put down everyone's responses. At least try to get 10 responses and till then you should have a good idea of why that particular product doesn't exist.