Warning: Undefined array key "visitor_referer_type" in /var/www/vhosts/wordinf.com/core/app/libraries/Core.php on line 98 Leonhard Euler - The kind of knowledge which is...
The kind of knowledge which is supported only by observations and is not yet proved must be carefully distinguished from the truth; it is gained by induction, as we usually say. Yet we have seen cases in which mere induction led to error.