An atheist organization is hoping its new billboard will challenge the way some Calgarians think.

The Centre for Inquiry has installed an ad on Edmonton Trail for six months that reads, "Praying won't help. Doing will. Without God. We're all good."

The organization says the campaign has an important message to share.

"We all are inherently moral," said executive director Nate Phelps. "It is a function of what we are born with and what society teaches us. So that's what the message is, that we can be good without ... a belief in God."

He says the Centre for Inquiry is based on science and challenges beliefs based on faith or lack of scientific proof. 

"We believe that there is a right way to discover the truth, which is the scientific method, and everything else out there can lead to ideas and behaviours that are counterproductive or destructive to society," said Phelps.

Calgary is the third city to post the ads.

The campaign faced some difficulty in Vancouver when a company that owns billboards refused to post the ads. A competing company later decided to put them up.

"The hope is that there are going to be some people who are going to look at this and it's going to challenge their ideas, the beliefs that they hold in their mind and that they act on and that we can get movement in the direction of society making better choices — more informed choices," said Phelps.

Phelps says an anonymous donor who supports free speech is paying for the ads in Calgary.