Complex sentence: Understanding mechanism and understanding causality go hand in hand; children need to understand that there are causes and effects in the world in order to understand how mechanisms can operate, and this knowledge in turn allows them to understand specific causal relationships.
Split into simpler sentences: Understanding mechanism and understanding causality go hand in hand; children need to understand that there are causes and effects in the world in order to understand how mechanisms can operate. This knowledge in turn allows them to understand specific causal relationships.