Investing in the stock market can be challenging, particularly in a world where the future is unknown, and the markets are constantly shifting. Nevertheless, there are ways to make informed decisions and manage risk even in such an unpredictable environment.

As Howard Marks has noted, "investing consists of exactly one thing: dealing with the future," and it's important to accept the fact that the future is never certain. Thus, a probabilistic mindset is essential when it comes to investing.

One way to develop a probabilistic mindset is by engaging in thought exercises. For example, consider the following scenario: You've invested in a company that you believe has a 60% chance of success, but you discover that a new competitor has emerged, reducing your confidence in your investment to 40%. Do you sell your shares or hold on?

This exercise demonstrates the importance of considering probabilities and being willing to adjust your beliefs and actions based on new information.

As Nassim Taleb, author of "The Black Swan” has said, "The problem with experts is that they do not know what they do not know, and don't care that they don't know it." Being willing to change your mind and adjust your investment strategy based on new information is essential in a probabilistic world.

Another key factor in investing is understanding risk. As economist Harry Markowitz has noted, "Risk means more things can happen than will happen." In other words, there are always unknown unknowns that can impact your investments, and it's important to manage risk through diversification and a well-defined investment strategy.

Cliff Asness emphasizes the importance of diversification, stating, "Diversification is the closest free lunch you can get in finance." By spreading your investments across different sectors and companies, you can reduce the impact of any single event or trend on your portfolio.

Ultimately, investing in the stock market requires making decisions under uncertainty and managing risk through a probabilistic mindset, diversification, and a well-defined investment strategy.

As Kahneman and Tversky have noted, "We are not comfortable thinking in terms of probabilities, and we often resist it, but the world is probabilistic, and we must become more comfortable with it."