[eitally]

The safest and best approach, as far as my limited parenting & school volunteering experience has demonstrated, is to go in with the assumption that the kids are just as smart as you and that they only suffer from lack of life experience.

Yes, the fact base kids have is limited due to limited experience & education, but they are able to learn and reason just as well as adolescents and adults, and should be treated like that. What they need is exposure to reasoning methods, clear explanations of logical fallacies, and necessary background information that will help them both articulate complex thoughts and set context for their reasoning.

I would argue that, in many cases, kids are "smarter" than adults because their lack of experience also correlates to increased creativity. Rather than pattern matching based on experience they'll frequently try out-of-the-box methods to solve problems -- this should never be discouraged.

[tetromino_]

This may be the correct attitude towards school-age kids, but is plainly wrong when dealing with toddlers. For one thing, very young children are usually unable to empathize. So they are unable to understand why it's bad to seize their cousin's toy, they are unable to understand why it's bad to leave a mess for someone else to clean up - they can be taught a set of rules of behavior, but they won't really get the principle underlying those rules until their brain grows more and develops the ability to imagine themselves in other people's shoes.

[tremon]

From around 8 years old (depending on the child), this is probably an accurate assumption. Many children younger than that do not have a fully-developed theory of mind to understand different perspectives on the same issue. This may not matter too much for natural science topics, but it does impact their ability to comprehend social or political issues.