"Whichever theory we adopt to give a rational explanation of human existence, that theory must take into account and explain the mental nature we see at work in all modern communities"

This quote by Arthur Keith suggests that any theory we use to discuss human presence must have the ability to describe the mental nature of modern-day communities. This implies that the psychological nature of human beings is an important consider comprehending our existence. It suggests that our mental nature is a crucial element of our identity and that it must be considered when trying to explain our presence. This quote also indicates that our mental nature is something that is shared by all modern-day communities, recommending that it is a universal trait of humanity. This quote encourages us to consider the mental nature of human beings when trying to describe our existence, as it is an essential element that ought to not be neglected.