Are monopolies inevitable under capitalism?

Grégoire Canlorbe: According to a popular opinion, left to its own devices, capitalism inevitably tends to a monopoly economy — an economy in which there is no competition. In a monopoly environment, the dominant companies can freeze competition and entrepreneurial initiative.

In what circumstances may some form of monopoly be inevitable?

First, there is only one firm operating in the market. Second, there are high barriers to entry. These barriers are so high that they prevent any other firm from entering the market. Third, there are no close substitutes for the good the monopoly firm produces.