We shouldn't deny the 'existence' of these problems. [=we shouldn't deny that these problems are present or real]
long before the country had 'come into existence' [=begun to exist; come to have actual being]
I owe my very 'existence' [='life'] to their courage. [=I am alive because of their courage]
(..) MARTY: I haven't told you about... DOC: One shouldn't know about his own destiny. - You don't understand. - I do. If I know too much I endanger my own existence... ...just as you've endangered yours. You're right. Let me show you my plan for sending you home. (..)1985 Back to the Future
(..) again of your brother. Just as I thought. This proves my theory. Look at your brother. MARTY: His head's gone. It's like it's been erased. Erased from existence. They really cleaned this place up. Looks brand-new. DOC: According to my theory, you interfered with your parents' first meeting. (..)1985 Back to the Future