[btilly]

The major flaw in your reasoning is that you've failed to identify a correlation between thinking positively and surviving cancer. Given that several large studies have also failed to show a correlation, I am forced to doubt the therapeutic benefits of positive thinking for cancer.

That is not to say that there are no health benefits from optimism. For instance there is evidence that it helps with the risks from cardiovascular disease. But it is far more dubious as a treatment for cancer.