If we were to experience a physical attack it would be instinctual to defend ourselves.
If someone says we are wrong about something, defence also seems to be the natural response.
It's of course logical that we protect our physical self, but why do we feel attacked when someone simply disagrees with us? Why are ideas and beliefs so important that we rise to defend them?
What's happened is that our ideas and beliefs have become associated to our sense of who we are, almost as much as our body has!
This sense of self is commonly termed; Ego.
From a very early age our mind begins to come to terms with the needs of the body. This is the earliest formation of the ego structure. Then gradually, as we become increasingly aware of the world, the ego develops complexity. It starts acquiring information about life and what will make it feel secure and safe, attaching a sense of importance to objects, including objects in the mind like ideas and beliefs. So now not only has the body become, 'my' body that I must protect, but so too other physical and mental 'possessions' become part of the sense of who and what we are.
This would not cause any great problems if the ego stopped at only what was needed, but for some reason it seems to run out of control, continually grasping for more, then jealously protecting all that it 'owns'.
All kinds dysfunctional behaviour can result, including incredibly selfish or hurtful thoughts, words and actions. Every cruelty and all wickedness that humans perpetrate stems from this.
As we become aware of the ego function in us and can see how it is at the root of so much of our wrong thinking and behaviour - and how this causes us great suffering - we become highly motivated to attempt to rid ourselves of it.
This is no easy task because by the time we become able to 'see' it, ego is deeply embedded in our operating system. We're not even aware of the way in which it moves within us or how we tend to be taken over by it.
To begin, the best we can do is notice the ego in action and attempt to close down the program.
The ego-identified, ego-led 'unconscious' state is how we come to realise we have lived - full of the results of its actions that have caused tensions, anxiety, conflict and stress, but once we are familiar with the insidious ways of ego, just in the seeing of this, the process of eradication begins.