The second example sentence should say "read and write" not "read and right."

How can I apply potentiality to verb です?

人間の思想が不自然です。

I'm trying to say something like "human ideas can be unnatural/artificial"

thank you very much, that helps alot.

However, I'm not quitely talking about right or mistaken ideas. It sounds quite abstract but I'm writing about nature (自然) in a kinda philosphical way and I was trying to express that reality is all natural, but our ideas might not flow according to nature's way, of course that might be somehow equivalent to the concepts of truth and falsehood, but it was another way to say it, "unnatural".

In case "不自然な思想" is a valid concept, something like this would be right?...

現実は自然ですが、時に人間の思想が不自然です事が有ります。

??

is that the way to use ことがある with です verb?

The reason I didn't rewrite it with the 不自然 bit is that we (my Japanese friend and I) could not figure out a good way to translate the English into Japanese. Especially since it's abstract, as you put it, it's hard to make a direct translation.

Because of that, I used the 'mistaken' example not as a replacement, but as a way to explain that grammar point.

As for ことがある and です, you don't need to actually put in です. I think the best way (will double check) would be
...不自然ということがあります.

That takes the statement preceding it and turns it into a noun. Again, I think this works, but I'm not positive. I can say with certainty that you a)do not put です in from of こと, and b)you would not use あれる (I don't think I've ever heard someone say あれる in any context).

You might want to cross-post this in the site's forums (link at the top) - I haven't quite figured out how to get more eyes on these discussion pages, but more people will see a question in the forum.

in the conjugation table, the example いそぐ becomes いそげる, but is そ supposed to be in red too?

oh ok, i guess i just don't understand then ... I was thinking that the そ in 急ぐ wasn't part of the verb ending and therefore wouldn't be a part of the change ...

Souldn't が be used instead of を？For exaple "手紙が読める", and not "手紙を読める". Potential forms do not have direct objects I've heard.

on Can A; be able to A (ability of the subject) example no 8 (しんじる).can you tell me why しんじる　became しんじられる. not follow the pattern (るーれる and its negatif form should it be しんじれらない) ?

For the second sentence,「彼は平仮名を読んだり書いたり出来る、片仮名は書けませんけれど。」 "書けません" should be highlighted. :P

My Japanese friend once stated, that the potential form of 一段 verbs is just ~れる (e.g. 食べれる). And even my text book (namely JFBP) agrees, that ~れる is sometimes used in colloquial speech. Although I have to admit, that is looks and sounds somewhat strange, for someone like me, who deals with linguistic terms like 未然形, 連用形 etc., it would make perfectly sense to simply add ~る to the 仮定形 of verbs. And it would be soo much easier. :-[ Anyway, I don't know how you think about it, but maybe it's worth a side note?

looking at the example sentence 「その女の子は突然猫に変身為ました！信じられない！」, the first exclamation point is the only thing highlighted - shouldn't the 信じられない be highlighted instead?