A few years ago Elon Musk made headlines by using his platform to mainstream the proposition that we actually live in an elaborate matrix-like computer simulation. The argument is fairly straightforward—if there's only one prime 'reality', and, further, if we assume that it's possible to simulate other pseudo-realities an infinite number of times within that reality, then the probability is that we live in one of the infinite simulations rather than the one non-simulation.
The argument that Cassius mentions above from Lucretius seems to apply equally here; if it were true that we existed in a simulation, then our knowledge could have no foundation. It's just a simulation experiencing itself as a simulation. And if our knowledge had no foundation, there would be nothing to justify the initial two premises of Musk's argument, rendering it self-defeating.
One does have to start somewhere. Epicurus starts with the senses. It's true that we have to accept that the information relayed by the senses is valid dogmatically. To start with the material, as reported by the senses, is to start with the obvious.
That answer might not be very satisfying, but unless you start somewhere, you don't get anywhere.
QuoteTo refute the solipsist or the metaphysical idealist all that you have to do is take him out and throw a rock at his head: if he ducks he’s a liar. His logic may be airtight but his argument, far from revealing the delusions of living experience, only exposes the limitations of logic.
—Edward Abbey