In Priestly's earlier life, as a young boy, he was surrounded by socialism and socialist ideologies.
His father was a passionate socialist leading to these views being absorbed from a young age.
Priestly fought in WW1, yet he was openly scathing of the institutions, he said:
"The British army specialised in throwingmen away for nothing"
His uncensored political voice is evident within the play.
Priestly's contribution in WW1 led to his realisation of the vast inequalities that plague society.
In 1945, Priestley was a co-founder of the commonwealth party.
This was a socialist party that favoured equality, morality, and common ownership (less should be privately owned, more owned by the public).
The commonwealth party helped galvanise (shock/excite into taking action) support for the Labour Party's landslide victory of 1945.
Link to play: Priestly's strong socialist ideologies are personified through the Inspector.
The Inspector acts as a moral compass for the Birlings, aiming to guide them away from their dehumanising capitalist worldwide views by introducing them to socialism.
Thus, Priestly vilifies capitalists, particularly through Mr. and Mrs. Birling, to make socialism seem a more favourable societal approach.