Paranoia is currently defined in most dictionaries as an irrational suspicion of others. A more complete definition of paranoia would be the presence in one’s mind of any persistent irrational belief – any persistent belief that something is true when it is false – or any persistent belief that something is false when it is true. When a person believes something to be true (or false), and the belief is supported by observation and reason, then the belief is not paranoia. Rational belief is based on truth whereas paranoia is based on untruth. To prove paranoia one must first prove that the belief in question is untrue.
Most people exclusively think of paranoia as “seeing” a threat that isn’t really there – this is suspicious paranoia – it’s the man who irrationally believes “someone is out to get me” when it is not true. There is however another type of paranoia – another type of irrational belief – which is intellectual blindness or blind paranoia. Those who suffer from blind paranoia can’t see a threat that really is there – it’s the man who believes someone is not out to get him when in truth someone is out to get him. Thus the blind fool is as paranoid as the suspicious fool.
Paranoia should be equated to any persistent irrational belief, so a definition of paranoia based only on irrational suspicion is incomplete since it only addresses a subset of irrational belief. It is self-evident that there are only two possible types of irrational belief – one where a person perceives something that isn’t there – and the other where a person can’t or won’t perceive something that is there. The first instance can be rightly called suspicious paranoia and the later blind paranoia (or denial), but it doesn’t really matter which name one uses as long as one understands the concept of irrational belief which, in the end, can only be expressed in these two opposite ways.