Can we ever really know anything?

Can we ever know something without doubt, or can we always doubt things?<br><br>We have an opinion of the world, but how much of it is true? We can't always be 100% certain. We can never be 100% certain that something is true, and we can never be 100% certain that it's not true. <br><br>Even if we see something with our own eyes, we can still question whether it is what it seems. What if it is just a simulation and it is not what it appears to be? <br><br>The only thing we can be 100% sure of is that we ourselves exist, but how do we know that? What if we're all just brain in a tank simulations and our whole lives have been a simulated reality? <br><br>I don't think it's possible to be 100% certain of anything, is it?