The main point is that there are a number of different axes along which "severe", "major" or "clinical" depression is said to differ from ordinary sadness, and that the qualitative distinction is used to justify all of these.
The main ones are
1) Depression (unlike sadness) is not caused by circumstances that cause a person to be unhappy.
2) Depression (unlike sadness) can only be cured by addressing to root (medical) cause of unbalanced brain chemistry.
3) Depression (unlike sadness) either is not curable, only the symptoms can be cured, or people who recover are prone to relapse.
>Have you ever experienced severe depression (i.e., the type that prevents you from getting out of bed for months or causes you to be hospitalized)? Because it's absolutely fucking awful.
No, but maybe I've experienced things just as bad? I don't really know, but I also don't know how you claim to be able to compare your experience to mine.
I'd love some clarification of where you're going with this hypothetical, because right now it sounds like you're denying the experience of a whole lot of people in a whole lot of pain, without having much of a point.
It's a logical fallacy to think that people do/should only make arguments with some end goal. My goal is to express my opinion on the nature of mental illness. Another fallacy is that arguing that "X is true" can be immoral, because of X were true, then some immoral consequence would follow. If I am right, we should still be just as compassionate towards other people's problems.
You can be compassionate and understanding towards someone's problems without categorizing those problems as a medical illness. Similarly, you can use this categorization as an excuse not to be compassionate, e.g. treating a person as irrational or untrustworthy because they have had a mental illness in the past.