JF

 You may be thinking of this quote that is often attributed to Pulitzer-winning science writer Jon Franklin:

“The human being is a mechanism, and in this mechanism there is a mechanism which prevents the human mechanism from seeing its mechanistic nature.” 

I should note that while this quotation is widely repeated online and attributed to Jon Franklin, I could not find a reliable primary source (such as one of his books or articles) confirming the exact wording. 

If you’re looking for a verified Jon Franklin quote about humans as mechanisms, one documented passage from Molecules of the Mind is:

“…while the brain was a mechanism far more complex and delicate than the finest of clocks, it was nevertheless a mechanism.” 

If you’d like, I can also help track down the original source of the first quotation.