If you're talking to yourself, you exist. That you ask would indicate it's a curious skepticism of an existence. That you ask the world you perceive if it perceives you seems like a conflict of self-definition between the perceived and the perceiver.
Therein lies loneliness, loss of the thread of life that energizes us all, that reproduces our cells from the same cosmic dust and enables us to have at it as we mayhap.
Alone, I observe a world needless of my observations to carry on and I feel free as I can imagine being.
In the company of men I am trapped by supposition that I exist only where I, who I know myself to be, impinges on their unique sensitivities and agendas, waiting for that wink to acknowledge the unspoken link of being different eyes of the same cosmic observer. Without knowing oneself, one is held in thrall to rumor, reputation and gossip.