Hmmm

[one_mad_cow]

Is it actually possible to not be able to "fight your way out of a paper bag"?

[bernardo]

Yes, if you are a tiny baby or Stephen Hawking or paralysed or dead or an ant or (etc.)

[Mr.Ix]

We have some very strong and thick paper sacks in our garage that I can bearly tear, so I reckon they could be tough. ;)

[Loosehead]

This was once tested on one of those weird science shows on kids TV. They had a top boxer and a large paper bag, scaled up to have the same proportions as one of the white bags for loose sweets. The boxer failed to punch his way out of it. 

[Clayhead]

Yes, I recall the boxer as Henry Cooper

[Jellicoe]

I think that the Boxer in question was Freddie Mills