If it is true that...

The bourgeoisie has called into existence the men who are to wield these weapons — the modern working class, the proletarians

Then it must be true that...

As the bourgeoisie develops, so does the proletariat, a class of laborers who live only as long as they find work and who find work only as long as their labor increases capital

If it is true that...

Modern bourgeois society has established new classes, new conditions of oppression, and new forms of struggle

and

The bourgeoisie has called into existence the men who are to wield these weapons — the modern working class, the proletarians

Then it must be true that...

As the bourgeoisie develops, so does the proletariat, a class of laborers who live only as long as they find work and who find work only as long as their labor increases capital

If it is true that...

As the bourgeoisie develops, so does the proletariat, a class of laborers who live only as long as they find work and who find work only as long as their labor increases capital

and

The proletariat is recruited from all classes of the population

Then it must be true that...

With its birth, the proletariat begins its struggle with the bourgeoisie