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.