Regards, I would like to know about a particular usage of the preposition 'on'. The sentence
What a pity, his house was on fire.
means that the house was damaged by a fire.
But the preposition 'on' is used for time and place (surface). What explanation for this?
Now what about these two sentences :
The paper will catch with fire.
The paper will catch on fire.
Which is the correct sentence?
I would appreciate thorough and compact analysis. Thanks.