Tell me how free will doesn't exist
A neurobiologist could explain this better than I could: but when we go deep into the structure of the brain, we understand that our actions, our emotions and our thoughts.. or mainly what we call "conscience" are regulated by the biological connections that are existing and created each seconds of our lives in our brain:
The simple act of clicking on a picture on the internet is conditionned by thousands and thousands of material biological neural prerequisite already existing in our brain: our history with said picture, our level of interest for the subject, the level of satisfaction that we know will result of this click, the level of fear that could result from this click, the ammount of physical effort that will demands this click, etc. And those thousands and thousands of prerequisite are existing because of thousands and thousands of others biological prerequisite that are in reality physical connections between different parts of our brain and our body. (and I'm not even taking into account the impact of the environment on a macro and micro scale on those prerequisites)
This means that a simple act of clicking on a picture on the internet will be the results of millions of parameters and "calculations" that are completely invisible on a surface level for us. In fact, the physical signals and therefore actions put in motion to click on a simple picture will be put in motion slighly before we even take conscience of the need to click on the picture.
Which means that there are no "choices", but the illusion of a choice.
In reality, free will, as people USUALLY defines it, is a materialistic impossibility in our current understanding of the universe. Because for this type of free will to really exist, it would means that the consciousness of an action preceeds the physical neurobiological interactions in the brain that will make us take conscious of our willingness to do said action.
In short, the presence of free will would means that we could create something out of nothing out of pure will. Which would go against the first law of thermodynamic. A foundamental law of the universe.
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However, the fact that freewill doesn't exist doesn't mean that we don't and that our actions or our lives are meaningless. For now, we must live in the illusion of freewill as society is not ready for a full switch yet.. but we might have to change that one day. For this moment to arrive smoothly, we must understand clearly the nature of the universe and the nature of life and the nature of our behaviors.