Non Sequitur
A non sequitur is a type of logical fallacy where the conclusion or statement does not logically follow from the previous argument or premise.

Non sequitur is an abrupt shift in topic or a statement that lacks a clear, logical connection to what was discussed before. In the context of communication and argumentation, a non sequitur can be unintentional, representing a failure in logical reasoning. It can also be used deliberately for rhetorical effect or humour, where the unexpected or unrelated statement creates surprise or amusement.

For instance, if someone is discussing the benefits of a healthy lifestyle, and another person responds with something completely unrelated, like talking about the weather, it would be a non sequitur.

Personal Incredulity
Personal incredulity is a logical fallacy where someone concludes that a statement or claim must be false because they personally find it difficult to believe or comprehend.

Essentially, personal incredulity is dismissing an idea as untrue based on the individual's inability to imagine or accept it, without providing substantive evidence or logical reasoning.

For example, if someone says, "I can't believe that aliens exist because it seems too unlikely to me," they are committing the fallacy of personal incredulity. The disbelief or scepticism of the individual doesn't serve as evidence against the existence of aliens.

In discussions and arguments, it's essential to recognize and avoid personal incredulity, as it doesn't contribute to a rational evaluation of the evidence or the merits of a claim. Encouraging open-mindedness and considering evidence and reasoning are crucial for constructive and logical discussions.