Somehow, it has happened that we live in a culture where technologies are a matter of fashion and objects of almost religious worship (think about tech evangelism, "changing the world," and tabs versus space wars). AI is on the peak of its popularity now. We often say, "Everybody does machine learning, so let us also build a neural network into our product and advertise it as artificial intelligence!" Undoubtedly, machine learning is an excellent hammer, but not all things around are nails. As you probably know, any product gets better if you add Bluetooth to it. However, this rule does not hold true for machine learning. The author of this book believes that there were too many great services that became inconvenient and unpredictable when machine learning was added to them. Rephrasing the famous quote by Jamie Zawinski about regular expressions: