double negative?

[katerina.pata]

Dear teachers,
This is a correct sentence taken from an English textbook.
You must have upset him somehow-he can't be angry for no reason.
How comes that it is not considered to be a double negative?
Thank you very much for your help.KP

[Soup]

The phrase no reason (at all) is an idiom meaning without reason (Cf. sans raison French).

[Raymott]

Dear teachers,
This is a correct sentence taken from an English textbook.
You must have upset him somehow-he can't be angry for no reason.
How comes that it is not considered to be a double negative?
Thank you very much for your help.KP

I would consider that to be a double negative, used correctly.
The prescriptive rule against double negatives applies only when a double negative is used to mean a single negative.

[katerina.pata]

Thank you very much Mr. Raymott for your due time and attention!
I do not fully understand what it means that a double negative can be used to mean a single negative.
Please, could you just recommend a source where to learn more about it??
I do not want to keep you...

[Raymott]

Thank you very much Mr. Raymott for your due time and attention!
I do not fully understand what it means that a double negative can be used to mean a single negative.
Please, could you just recommend a source where to learn more about it??
I do not want to keep you...

There is not much to learn.
You said: How come that it is not considered to be a double negative?
From which I concluded that you thought it shouldn't be there because double negatives aren't allowed in English (If I'm wrong about why you asked that, please correct me).

My response was that it was not double negatives per se that are the problem. It is using them to mean a single negative, such as:
"You don't love me no more" to mean "You don't love me any more" = "You no longer love me." (One negative needed, and one used).
"I ain't gonna work no more" for "I'm not going to work any more"
"Don't nobody tell me nothing no more" (A quadruple negative, meaning "no one tells me anything anymore).
These last sentences are wrong in Standard English.
But if you mean a double negative, "He did not tell me not to do it, therefore I did", this is a normal acceptable sentence because the sentence calls for two negatives.

Do a search for "double negatives" anywhere if you want to know more.

[katerina.pata]

Thank you very much Mr. Raymott! What an excellent explanation...I thank you and admire you for helping 'us' amateurs..How patient you must be...

There is just one more thing I am not sure about- I wrote- How comes that it...?
In your reply you used- How come that it....?
Did I make a mistake there or are both options acceptable?
Is there any connection to the question- How dare he? I am aware of this construction being grammatically correct but I am not sure either...
Thank you very much in advance.
KP

[Raymott]

Thank you very much Mr. Raymott! What an excellent explanation...I thank you and admire you for helping 'us' amateurs..How patient you must be...

There is just one more thing I am not sure about- I wrote- How comes that it...?
In your reply you used- How come that it....?
Did I make a mistake there or are both options acceptable?
Is there any connection to the question- How dare he? I am aware of this construction being grammatically correct but I am not sure either...
Thank you very much in advance.
KP

Yes, it's "how come". It's invariable. In fact, it sounds subjunctive, in which case, it would be similar to "How dare he?"
They could be written "How does it come that..."; "How does he dare to..." which use "do" as an auxillary.
In any case, whether they derive from the subjunctive or not (which I'm not 100% sure of), "How come" always takes that form.

[katerina.pata]

Mr. Raymott,
thank you very much.
KP