I've completed an immersion study into Penington's use of the phrase 'thing itself." This study demonstrates Penington's faith anchored solidly in the presence of Christ, the inward Light, as sufficient knowledge and experience as opposed to outward rationalizations about Presence and the words of the bible. 

The gift of the thing itself as the sufficient Rule, Principle, Discipline, Code, or Practice in all activities of daily life is the salvation of men and women.

Below is a sampling of Penington's use of the "thing itself" followed by links to all of Penington's uses of  the "thing itself" from the four volumes of  the "Works of Isaac Penington." His words are treasures.

Take not up a rest in openings of things, though by the true key. Take heed of overvaluing that kind of knowledge ; for that part which overvalues that knowledge will presently be puffed up with it: but there is a more excellent and safer kind of knowledge to be pressed after, which is a knowledge of things by receiving of them. There is a knowledge of things by the Spirit's opening the words which speak of them, or by inward, immediate prophecies from the word of life in the heart. This is an excellent knowledge, and not to be found in the earthly part of man : yet the earthly part (when this knowledge is given) is very apt to be swelled and exalted with it; but then there is also a knowledge which ariseth from the gift of the thing itself. This knowledge is very precious, and much more full and certain than the other, having the nature and immediate power of life in itself, and so is perfectly able to preserve. As for instance, to make it more plain: there may be a knowledge of justification, by the Spirit's opening the words written in scripture concerning justification, and the blood of sprinkling; and this is a good knowledge, where there is a true opening of it from the Spirit : but then there is a knowledge by feeling of the blood of sprinkling in the heart, and by seeing with the new eye the way of its justification; and in this knowledge is the power and the cleansing of the life received, which in the other was but spoken of. Therefore rest not in opening of prophecies, or true meanings of these things (though this kind of knowledge is very excel lent, and hath been very rare), but wait to feel the thing itself which the words speak of, and to be united by the living Spirit to that, and then thou hast a knowledge from the nature of the thing itself; and this is more deep and inward than all the knowledge that can be had from words concerning the thing."

Pages 322, 324

From Volume One:

https://docs.google.com/document/d/16aFapDikvKqhXp4IMaroO4RKDuLlXfu...

From Volume Two:

https://docs.google.com/document/d/17MxHu2xhySGBzRzTTEY79jJAS0IE7mu...

From Volume Three:

https://docs.google.com/document/d/18D-hoiUvXPeLzn2jALfCOGVNSd6oZmk...

From Volume Four:

https://docs.google.com/document/d/18alnQUd3By08br2z1aPVw5J5n7f3rdC...

Blessings and Blessedness,

Keith