As usual, note that Positive Thinkers should be criticized.
I think this speaker ignores some painful evidence. E.g., he says that money received is always in proportion to service. However, some unfortunates work honestly and get screwed by society.
Furthermore, note that even if “success follows positive thinking” IS a law, that doesn’t undo other laws, such as the 2nd Law of Thermodynamics.
Certainly William James was right when he said that humans can change their attitudes, and thereby change their lives. A human life is a complicated phenomenon, and many things can change to make a big difference in a human life. There are many ways in which a human can honestly say, “My life has changed for the better.”
This recording was made in the USA, in the 20th century, at a very prosperous time. I don’t know that positive thinking in the USA would be equally effective if exercised today.