Bacon has warned us that selfishness should be checked, in the context of a prince-servant relationship.
Of course he is dead but here "has" is used.
Why? He warned us right? He warned us in the past many many years ago. Not recently.
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In the humanities generally we regard old authors as still present through their works. You will rarely find a scholar or critic writing that “”Homer said” or “Shakespeare wrote”; it is almost always “Homer says” and “Shakespeare writes”. The same is true of scholarly writing: “McCawley (1971) distinguishes four varieties of categories of use of the perfect.”
This is not the case in the social sciences; the APA style sheet calls for even very recent papers to be referred to in the past.
Please note that the "Present perfect" tense says about either past and present.
For instance, I may say (many times) :
"You should wash your hands before eating!"
and some time later, I see you're eating with dirty hands, so I tell you:
"I've told you many times that you should wash your hands before eating, but you never take care!"
Obviously I've told you something in the past, but I use the Present perfect to this aim. Indeed the verb has happened in the past but the effect still exists.