Justin Bieber has encouraged fans to step outside their "comfort zone" and question the meaning of life.

The 22-year-old singer turned philosopher on Monday (04Jul16) when he posted a lengthy message on his Instagram page for his 73.6 million followers.

"It’s crazy how some people don’t even question or ponder the reason for their existence and are okay going through the motions. We don’t live to die. We have purpose and meaning! Step outside your comfort zone and challenge your friends by asking those tough questions like what do you think the meaning of life is? What do you think your purpose is?" he wrote.

Justin has courted controversy since he first shot to fame at the tender age of 13. But he continued his post to insist that while his fans don't have to share his beliefs, they should be open to the idea of there being more to life.

"I’m not saying you have to believe the same thing I believe but at least have the discussion..." he wrote. "Sometimes it can be scary opening yourself up to what can come from those conversations, and I think it can be easier sometimes to just avoid and not think about it! But I think it’s worth it!!!!"

The Sorry singer has been displaying somewhat concerning behaviour in recent months, including banning fan selfies because he feels like "a zoo animal", halting meet-and-greets backstage on tour and being spotted walking barefoot in a park in May (16).

He has also made a habit out of sharing his musings, apparently written on his phone's Notes app, on Instagram.

Thoughts posted last week (ends03Jul16) included Justin writing: "I don’t always feel God’s presence, I feel it may be human distractions or maybe I’m letting lies detour me from accessing it. Regardless it doesn’t stop me from seeking. Although it is frustrating I’m reminded that relationships take work, even with God!"

He also posted: "I’d rather be lonely than to hang out with just anyone to not feel lonely. They have to be awesome or I’m Netflix and chill."