The concept of "not putting all your eggs in one basket" is a well-known investment strategy that is also referred to as "diversification." The idea behind diversification is to spread your investment capital across a variety of different asset classes, such as stocks, bonds, real estate, and commodities, rather than concentrating all your investments in a single asset class or a handful of individual stocks.

The goal of diversification is to reduce the overall risk of your investment portfolio. By investing in a range of different assets, you can reduce the impact of any one asset's poor performance or market downturns on your entire portfolio. This means that if one of your investments loses value, the other investments in your portfolio may be able to offset those losses, leading to a more stable overall return.

There are several proven theories that support the practice of diversification. One of the most well-known is the "Modern Portfolio Theory," developed by economist Harry Markowitz in the 1950s. The theory suggests that investors can minimize the risk of their portfolios by constructing a diversified mix of assets with varying levels of expected risk and return.

Another important theory that supports diversification is the "Efficient Market Hypothesis." This theory suggests that markets are highly efficient, meaning that all relevant information is already reflected in the current price of a security. This makes it difficult to consistently outperform the market by picking individual stocks, and instead encourages investors to focus on constructing a diversified portfolio.

In summary, diversification is a proven investment strategy that can help investors minimize risk and maximize returns over the long term. By investing in a variety of different asset classes, investors can reduce their exposure to any single market downturn or poorly performing asset, leading to a more stable and consistent return on investment.