For Braudel there is no single Mediterranean Sea. There are many seas—indeed a "vast, complex expanse" within which men operate. Life is conducted on the Mediterranean: people travel, fish, fight wars, and drown in its various contexts. And the sea articulates with the plains and islands. Life on the plains is diverse and complex; the poorer south is affected by religious diversity (Catholicism and Islam), as well as by intrusions – both cultural and economic – from the north. In other words, the Mediterranean cannot be understood independently from what is exterior to it. Any rigid adherence to boundaries falsifies the situation.