I wonder if you guys are as tired or reading replies like this from me- as much as I get tired of making them. lol
Once again, we are mixing two different things.
A Magnum Opus has two different (accepted) meanings.
1) A work so great that THE ARTIST can not surpass it IN THEIR MIND....
2) A Great Work that goes on to define the artist and becomes what they are best known for BY OTHERS.
The statement that an artist strives to make a 'Magnum Opus' means they want to keep improving - and keep improving until they tap their ULTIMATE potential and create a work they can never best. It is a paradox. No artist wants to reach, or imagines themselves reaching a point where everything they do isn't as good as something they've already done.
That is a nightmare.
Nothing worse than believing you are doing your BEST work ever! - something incredible and new and self-defining and the/your audience doesn't respond and thinks your current efforts are getting worse - and your old(er) stuff is way better.
YOU think it's your greatest work- everyone else does not.
The confusion comes from asking....
Should your BEST and BIGGEST and Most EPIC Thought Out idea be the one you start with?
Depends.
Did you master your craft enough to Eliminate the technical flaws?
Have you created enough work to understand the demands that come with creating work(s)?
Since the answer is usually NO - it's a safe assumption that EVERYONE should put some work in before starting their super epic. The misleading part is that many artist's FIRST WORK to arrive is NOT the first thing they ever worked on or created. But, it usually has the benefit of the most time and concentration. Years and years of being edited and re-worked and critiqued. And their second idea has WAY less time to mature so it seems like they lead with their best.
I need to wrap this up.
All the weirder arguments about this Magnum Opus thing are from people who haven't created a lot of art or finished any projects. When you build up a body of work or just create for a while, you realize that you cannot control or predict OTHER PEOPLE'S REACTION TO YOUR WORK/ART.
Things you spend HOURS working on perfecting are just glanced over and things you doodled or knocked out without thinking- are very effective. Ideas that have marinated for YEARS are just 'cool' to your readers and a quick idea that just popped in your head makes the story gel for them.
You never know.
You can never know.