Is nihilism the logical extreme of atheism?

[Chas]

God is so good that the definition has to come from him. One thing you can be sure of.

Because you say so? Oh, sure. I'm soooo convinced.

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No, he is goodness, otherwise he couldn't be him.

That is circular, you silly hobbit.

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Just to be clear, my definition of nihilism is very broad: holding that all values are baseless and that nothing can be known or communicated.

This takes me to my third component needed to counter nihilism: significance.

Significance refers to the relationship between a signs, or signifiers, and that to which the signs refer (the signified). So when people say that life has significance, then they are essentially claiming that their being and actions are signifiers that point to something external to them.

Signs are physical and include material forms, like letters, images, and artifacts; structured events, like music and speech; or some combination of both. The meanings of the signs are what people assign to otherwise meaningless things. For example, in traffic a blinking red light means ‘stop’ only as a matter of convention. Physical things in and of themselves do not have meaning without an interpreter.

Every atheist I know assumes that the brain adequately serves as the interpreter of signs. There is a problem with this assumption. Brains are themselves sensible objects performing material processes and like all other physical things have no meaning.

Neural correlates are like abacus beads that require the interpretation of a knowing subject. The brain cannot act as the interpreter of its own physical states because that makes an empty self-referential circle. Nor can one part of the brain serve and the interpreter of another, since the first would itself require interpretation from a second, the second by a third and so on, i.e. an infinite regress. Nor can the brain, as a whole, can be broken down into smaller and smaller interpreters, each assigning meaning to lesser and lesser signs. Even the smallest sign requires an interpreter no matter how tiny. You cannot build something out of nothing.

The above is how a God or gods provide a basis for value that atheism lacks: value is contingent on [a] non-physical interpreter[s].

Not brains, minds. Minds emerge from the functioning of brains.
And it is not a closed, self-referential system; it is an open self-referential system, continuously updated with fresh input and fresh connections and patterns.

Your 'explanation' assumes the existence of that for which there is no evidence. Dualism is an incoherent concept.