“Whether you function as welders or inspectors, the laws of physics are implacable lie-detectors. You may fool men. You will never fool the metal. That’s all.”

famous cat quotes
Bucky Katt's Big Book of fun, page 114
Bucky Katt

Source: Night-Thoughts (1742–1745), Night IV, Line 843.

"No one can get greedier for you than you. Because everything is in your sphere if you can deliver. It's so simplistic. If you can't deliver, you're out of there. It doesn't matter. And you can never fool an audience. You have to gain their trust by giving them the feeling that every time you perform you have done everything to present them your best. They will know. And that is the way they will stay loyal to you."
Source: Interview at the City University of New York's Arts & Leisure Weekend.
https://www.youtube.com/watch?v=PeKRKDoNXqY&feature=youtu.be&t=349

Source: The Lessons of History

Dogs
The Note-Books of Samuel Butler (1912), Part XIV - Higgledy-Piggledy

Source: Ars Magica (1989), Chapter 2 (p. 18)

This is probably the most famous of apparently apocryphal remarks attributed to Lincoln. Despite it being cited variously as from an 1856 speech, or a September 1858 speech in Clinton, Illinois, there are no known contemporary records or accounts substantiating that he ever made the statement. The earliest known appearance is October 29, 1886 in the Milwaukee Daily Journal http://anotherhistoryblog.blogspot.com/2009/02/fooling-people-earlier.html. It later appeared in the New York Times on August 26 http://query.nytimes.com/gst/abstract.html?res=F30817FF3E5413738DDDAF0A94D0405B8784F0D3 and August 27 http://query.nytimes.com/gst/abstract.html?res=F00E15FF3E5413738DDDAE0A94D0405B8784F0D3, 1887. The saying was repeated several times in newspaper editorials later in 1887. In 1888 and, especially, 1889, the saying became commonplace, used in speeches, advertisements, and on portraits of Lincoln. In 1905 and later, there were attempts to find contemporaries of Lincoln who could recall Lincoln saying this. Historians have not, generally, found these accounts convincing. For more information see two articles in For the People: A Newsletter of the Abraham Lincoln Association, "'You Can Fool All of the People' Lincoln Never Said That", by Thomas F. Schwartz ( V. 5, #4, Winter 2003, p. 1 http://abrahamlincolnassociation.org/Newsletters/5-4.pdf) and "A New Look at 'You Can Fool All of the People'" by David B. Parker ( V. 7, #3, Autumn 2005, p. 1 http://abrahamlincolnassociation.org/Newsletters/7-3.pdf); also the talk page. The statement has also sometimes been attributed to P. T. Barnum, although no references to this have been found from the nineteenth century.
Variants:
You can fool all the people some of the time, and some of the people all of the time, but you cannot fool all of the people all of the time.
You can fool all of the people some of the time, and some of the people all of the time, but you can't fool all of the people all of the time.
You can fool all the people some time, you can fool some of the people all of the time, but you can not fool all the people all the time.
Disputed

Travels with My Aunt (1969)