To determine whether there's a systemic decline or a flash crash that could be a buying opportunity, Cramer said investors should ask themselves questions about the state of the economy.
Before the crisis began in 2007, the Dow Jones Industrial Average closed at its peak pre-recession high of over 14,000 points.
Before the crash, Cramer said many who were following the mortgage market knew there were a lot of "unsound practices" occurring.
He explained that after calling numerous friends at different firms and mortgage bankers, he knew something was seriously wrong.
"The financial crisis gave us a once-in-a-lifetime bear market with true systemic risk, but that's the exception, not the rule," Cramer said.
Persons:
CNBC's Jim Cramer, Cramer
Organizations:
Dow Jones