Percipient

And that Pleasure does arise upon the exercise of every Percipient

Ethics 384 BC-322 BC Aristotle

And this will be, further, most perfect and most pleasant: for Pleasure is attendant upon every Percipient Faculty, and in like manner on every intellectual operation and speculation; and that is most pleasant which is most perfect, and that most perfect which is the Working of the best Faculty upon the most excellent of the Objects within its range.

Ethics 384 BC-322 BC Aristotle

Percipient is essentially a fancy-schmanzy term for an eyewitness rather than, say, an "expert".

Forbes.com: News Bill Singer 2012

a hitch in the Psychic Current which, colliding with a Dual Identity, had interfered with the Percipient Activity all along the main line.

Indian Tales Rudyard Kipling 1900

Now since every Percipient Faculty works upon the Object answering to it, and perfectly the Faculty in a good state upon the most excellent of the Objects within its range (for Perfect Working is thought to be much what I have described; and we will not raise any question about saying

Ethics 384 BC-322 BC Aristotle