Our or our's

I recently wrote the following phrase: "from God's perspective or from our's." I believe this is grammatically correct, but I'm curious as to why.

In Steven Pinker's book 'Words and Rules' he explains how a possessive "apostrophe S" can be added even to a long complex noun phrase. For example "This is the man who met me when I disembarked from the boat last Tuesday's umbrella". In this context you can even have words like "me's" make sense. For example "I stole the woman sitting opposite me's newspaper."

And I wondered if this same kind of process is happening in the above phrase. Or is something else going on? The perspective belongs to us, therefore it is "our perspective". Logically, shouldn't the phrase be "from God's perspective or from our"? But that doesn't sound right.

Can someone explain the difference between "our" and "our's" - both of which seem to indicate ownership.