the idea of war

[azz]

a. He was being driven mad by the idea of war and its consequences.
b. This book analyzes the idea of war and its consequences throughout history.

In (a) and (b) there is one idea and that is the idea of war plus its consequences.

c. He was being driven mad by the ideas of war and its consequences.
d. This book analyzes the ideas of war and its consequences throughout history.

In (c) and (d) there are two ideas: the idea of war and the idea of the consequences of war. The two ideas are viewed separately.

Are the sentences grammatically correct and meaningful?

Many thanks

[Alan]

(Not really a grammar issue, but...) The second two make no sense; singular only acceptable here, to mean 'concept'.