How perception really works
Start with the reassuring part: your senses are good enough that you can cross streets, recognize faces, and pour coffee without disaster. Evolution would not have kept them if they were badly unreliable. But 'good enough to live by' is not the same as 'a perfect mirror of reality,' and modern neuroscience is clear that perception is more of an active construction than a passive recording.
The influential view associated with neuroscientist Anil Seth is that the brain does not simply receive the world; it constantly generates predictions about what is out there and updates them against incoming sensory signals. What you experience is the brain's best guess. Seth calls this a 'controlled hallucination': controlled, because it is tightly reined in by real data, but a construction all the same. When the control loosens, as in optical illusions, you can catch the machinery making things up.
The classic doubts: Descartes and illusions
Illusions are the everyday proof. Straight lines look bent, still images appear to move, identical grays look different depending on their surroundings, and everyone falls for them, even knowing the trick. These are not failures of attention; they are built into how the visual system infers a stable world from ambiguous input.
Philosophers pushed this doubt to its limit long ago. In the seventeenth century Rene Descartes noticed that the senses sometimes deceive us, and reasoned that anything capable of deceiving us cannot be trusted as a foundation for certain knowledge. He used this 'method of doubt' to strip away everything questionable and look for something that could not be doubted, famously arriving at the fact of his own thinking. The lesson was not that the senses are worthless, but that they are not self-guaranteeing.
So can you trust them?
The practical answer is a qualified yes. For navigating ordinary life, your senses are remarkably accurate, and treating them as generally trustworthy is rational. The philosophical answer adds a caution: they give you a useful model of the world, not unmediated access to it, and that model can be wrong in ways you will not notice from the inside.
The healthy middle ground is neither paranoia nor blind faith. Know that perception is an inference, that it can be fooled, and that cross-checking, with instruments, with other people, with a second look, is how we catch its errors. Trust your senses the way you trust a very good map: rely on it daily, and stay open to the places where it does not match the ground.