Well, I want to make clear for learners that the concept of "verb conjugation (動詞活用)" is different from "tense (時制)." For example, many inflections like the -te form or -masu stem(-i form) don't have its tense. The -te form has many functions, as explained concisely in the wikipedia page I linked in my previous post, so "light command/soft imperative" is just one of the meanings even if it's put at the end of a sentence.
Grammatically, 書いています express different aspect from 書きます, not tense. Similarly, 書いて as a light command expresses a mood, not tense, and the passive form is a voice, not tense. For instance, 書いています vs. 書いていました or 書いている vs. 書いていた are different tenses.
I've never heard "nine levels of politeness." If it refers to formal, informal I, II, III or like that mentioned in the book, I don't agree with it.
e.g.
乾かす kawakasu
Imperative
INFORMAL
I 乾かせ kawakase
II 乾かしなさい kawakashinasai
III 乾かしてください kawakashitekudasai
FORMAL
お乾かしなさいませ okawakashinasaimase
I don't think 乾かしてください is informal, and there are many other expressions used for order/imperative like followings.
乾かしな
乾かしてくださいませ
お乾かしなさい
お乾かしになって
お乾かしになってください
お乾かしになってくださいませ
お乾かしあそばせ
お乾かしになりなさい
etc., etc..
Japanese verbs conjugate relatively regularly. There are only two irregular verbs, する and 来る. So, if you know how to make -masu stem or -te form of verbs, you would be able to get each expression listed as "Imprative" in the book without remembering all the expressions for every verb exhaustively. Whether it's 可愛がる or 乾かす, the expression the book called "FORMAL" is "お + -masu stem + なさいませ" after all.
可愛が
る kawaigar
u --> u is changed to i --> 可愛が
り kawaigar
i (-masu stem)
--> お
可愛がりなさいませ o
kawaigari nasai mase
乾か
す kawakas
u --> u is changed to i --> 乾か
し kawakas
hi (-masu stem)
--> お
乾かしなさいませ o
kawakashi nasai mase
(Note: These are examples of godan verbs. Ichidan verbs conjugate differently.)
Furthermore, it's inappropriate to call the -te form "gerund." Some textbooks use this term, but it often confuses learners. Refer to the following post for details.
Probably a linguistic curiosity rather than of any practicality. Usually when one combines the causative form and the passive form, the causative inflection is attached first to the root, then the passive. My question is, can you switch the process? e.g. 食べる, 食べさせられる, 食べられさせる. Also, if this...
In the early stage of learning, I think it's OK just to remember how verbs conjugate, especially basic forms like -te from, -masu stem(called i-form in the wikipedia), past from(perfective form), -nai stem(negative form) or potential form. It's not necessary to remember all the functions of each form, or the expressions using these forms like the ones written in the book.