"Una alucinación es un hecho, no un error; lo que es erróneo es un juicio basado en ella."

Simplified Meaning:

When someone experiences a hallucination, they are seeing or hearing something that isn't really there. This experience is real for them, even though it is happening only in their mind. The mistake happens when they believe that what they saw or heard is actually happening in the real world. For example, imagine someone hears voices speaking to them when no one else is around. The sound of the voices feels very real to them, which is the fact part. But if they think those voices are coming from real people in another room or are messages from the universe, that belief is where the error lies. In life, it's important to separate what we feel or think from reality. This way, we can make better judgments and decisions. So, if you ever have a very strong feeling or see something unusual, take a moment to think it through and consider other possible explanations before reacting or making conclusions based on that experience.