I've recently learned about the [OR] flag for mod_rewrite rules in an .htaccess file:

RewriteEngine On
RewriteCond ThisRule [OR]
RewriteCond ThisRule [OR]
RewriteCond ThisRule [OR]
RewriteCond ThisRule [L]
RewriteRule WriteThis

Does anyone know if this logic means that by default .htaccess rules are additive in nature?

RewriteEngine On
RewriteCond ThisRule
AND RewriteCond ThisRule
AND RewriteCond ThisRule
AND RewriteCond ThisRule [L]
RewriteRule WriteThis

If this is wrong, and they are not additive by default, what does one need to make them additive?  Is it the [C] flag "Chained with next rule"?

Thanks for the help!

-Alex.