Once you begin to question the significance of everything that happens in your life, you may realize that much of what you believe and value was not determined by you but by the people and culture around you.

In many cases, we grew up with good values, but everyone has its dysfunctions and obsessions. As adults, we need to reevaluate our values and beliefs and define what matters among a flood of useless information. Doing so will carry consequences for our own mental and emotional well-being. It will also determine the kind of footprint we leave in the world.

• René Descartes wrote in 1641, "I think; therefore I am." Descartes realized that we could never be sure that our perceptions are true - Your memories could be invented. Your room could be a hallucination. - But he knew with certainty that he existed. The fact that he could ask questions meant that he existed.
• About a hundred years later, David Hume showed that we could never be sure that our understanding of cause and effect is true. No matter how often something occured in the past, it is impossible to prove that it will happen in the future.
• Immanuel Kant built on Descartes' and Hume's ideas and said there is a difference between our perception of something and the thing in itself. I can see a tree, I can touch it and experience it, but I can never know the tree or experience life as the tree experiences life. I can only interpret the tree through my own senses.

All this is a way to show that whatever you believe you know to be true - you don't. Human understanding is too limited. We should then be careful what we choose to accept as true.

Philosophy then teaches us the fundamental techniques to find meaning and purpose. At some point in our lives, we have to ask and answer the following questions for ourselves.

• What is true?
• Why do I believe it to be true?
• How should I live based on what I believe?

Not answering these questions will result in a mental or emotional crisis, such as depression, anxiety, and an inability to find a sense of purpose.

The 21st-century life interfered with our ability to answer these questions:

• What I know to be true?. The flood of information (fake news, bad science, social media rumors, manipulative marketing, propaganda) is harder to understand if you can't trust information.
• How I know what is true?. Scandals of corruption are unveiled in every major institution. We are also more aware of irrational biases, prejudices, and wrong assumptions.
• How I should live based on what I believe?. Without knowing what is true or how to find truth, it is less clear how we should live. It creates a sense of existential anxiety and insecurity.

Philosophy is examining our understanding of reality and knowledge. Philosophy consists of three major branches:

1. Metaphysics - What is true about existence.
2. Epistemology - How we can know that it is true. Epistemology has given us science, logic/reason, economics, psychology, and other theories of knowledge.
3. Ethics - What actions we should take as a result of this knowledge. Ethics contains concepts such as democracy, human rights, the treatment of animals, and the environment.

When you order your thoughts into a coherent belief system, you are engaging in philosophy. To criticize philosophy, you must rely on philosophy.