Question: How should Buddhists explain why we do not believe in the existence of ‘souls’?
Answer: According to the Buddha’s teachings, there are no unchanging mental or physical entities called souls within anyone as we are changing from moment to moment, in terms of feelings, perceptions, intentions and awareness. In other words, there is no unchanging self. This is good news as it means we can spiritually change to be better persons, kinder and wiser, till we attain perfection of compassion for all beings and wisdom of all things by realising Buddhahood.
If there are unchanging essences called ‘souls’, it does not make sense to do better or worse in anything at all. As continuum of changing bundles of causally conditioned forms, feelings, perceptions, intentions and consciousnesses that are not totally the same or different from one moment to the next, we are constantly shaped and reshaped by our changing karma and attitudes. Further good news is that although we have no souls, the Buddha taught that all sentient beings have Buddha-nature, which is the everlasting potential to become Buddhahood, which is also True Happiness. If we practise the path he walked to Buddhahood, we will be able to realise it too.
Related Articles:
Why The ‘Same’ River Is A ‘Different’ River
https://thedailyenlightenment.com/2014/04/why-the-same-river-is-a-different-river
The Body Candle & The Mind Flame
https://thedailyenlightenment.com/2015/03/the-body-candle-the-mind-flame
How Are We Reborn Without Souls?
https://thedailyenlightenment.com/2015/03/how-are-we-reborn-without-souls
In your answer you say that there is no unchanging self. But isn’t it actually so that we are not these thoughts and feelings, but in (absolute) reality the unchanging observer, who just is?
There is only observing and no observer, thinking without a thinker, processing and no processor.