I am a serious person, and I value seriousness in others. That doesn’t mean I’m humorless or dour, mind you! I’m plenty goofy. It’s just that I approach things with a mindset that they should be valued for what they are. I strongly dislike sarcasm, I prefer to make my opinions clear, and I engage in discussion on the grounds presented.
I tend to value seriousness in others. Again, not “lack of humor” – in fact, if you can conduct yourself seriously while also maintaining a sense of humor I will regard you very highly. I crack jokes a-plenty, but not at the expense of being engaged with whatever I’m engaging with. Because I value others who take things seriously, I look for ways to evaluate intellectual seriousness.
One of the most certain ways to see if someone is an intellectually serious person is to see how they examine, present, or absorb counterfactuals to their own positions. If you think we should go about a certain project in a certain way – can you articulate what would change your mind? If you have a certain opinion – can you describe what led you to it, other than absurd claims of objective truth?
If you can’t? If you can’t wrap your head around the opposite view, then you’re likely not a serious person. You don’t have to agree with the opposite view, of course! But if you can’t see it, then you can’t engage seriously with any discussion surrounding the options.