Thank you for the clarification.

My argument is then that we will never have evidence that it exists because evidence is rational and objective and its very reality and/or value is trapped in the irrational subjective eye of the beholder.

Trying to boil it down into, say, patterns of neuron activations would be like trying to boil down or derive the "value reality" of the Mona Lisa by analyzing and cataloguing the light wavelengths reflecting off of it.

The claim that we will never have evidence that it exists says more about your need to not have your belief in its existence questioned than it does about the actual likelihood of evidence being found in the affirmative or negative.

Everything we know about what "evidence" is, is measurable.

So what of the unmeasurables?

I have no idea what you're responding to now.