First principles
From Wikipedia, the free encyclopedia
- First Principles is also the title of a work by Herbert Spencer.
In philosophy, first principles are a set of basic, foundational propositions or assumptions that cannot be deduced from any other proposition or assumption.
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[edit] First principles in formal logic
In a formal logical system, that is, a set of propositions that are consistent with one another, it is probable that some of the statements can be deduced from one another. For example, in the syllogism, "All men are mortal; Socrates is a man; Socrates is mortal" the last claim can be deduced from the former two.
A first principle is one that cannot be deduced from any other. The classic example is that of Euclid's (see Euclid's Elements) geometry; its hundreds of propositions can be deduced from a set of definitions, postulates, and common notions: all three of which constitute "First Principles".
[edit] Aristotle's contribution
Aristotle, author of the earliest surviving text on logic, formulated a principle that later achieved the historical distinction of being called the first principle as a proper name. It occurs in those of his writings that have come to be called the Metaphysics. The principle in Greek, and its transliteration, is (Meta ta physica, 1005b):
- "τὸ γὰρ αὐτὸ ἅμα ὑπάρχειν τε καὶ μὴ ὑπάρχειν ἀδύνατον τῷ αὐτῷ καὶ κατὰ τὸ αὐτό"
- "to gar auto hama hyparchein te kai me hyparchein adynaton to auto kai kata to auto."
and in English translation:
- "For the same (characteristic) simultaneously to belong and not belong to the same (object) in the same (way) is impossible."
This principle is the first expression of consistency in western thought. Any defining and reasoning in any language on any topic assumes it a priori. It cannot be doubted, as all doubting is based on inconsistency, which assumes consistency a priori.
[edit] Modern Western contributions
There have been many attempts in the history of Western metaphysics and epistemology to elaborate a single set of first principles. If a thinking person wants to make his or her knowledge internally consistent and make as much sense as possible, a set of first principles is necessary.
Some thinkers, especially in the 20th century, have savaged the notion that true first principles are available. In his Principia Mathematica, Bertrand Russell attempted to subsume all mathematical truths under the first principles of formal logic; however, Kurt Gödel launched a savage attack not only on Russell's system but on the very possibility of such a system, contending that any logical system that was consistent could not be complete, and any system that was complete could not be entirely self-consistent.
Likewise, Heidegger attacked something perhaps underlying the notion of first principle, that is, the need to represent the world, and the dualism that that task, in his view, entails.
[edit] In physics
In physics, a calculation is said to be from first principles, if it starts directly at the level of established laws of physics and does not make assumptions such as model and fitting parameters. This is also known as calculating ab initio.
For example, calculation or simulation of molecular electronics using Schrödinger's equation directly is an ab initio approach, since the equation is just a definition of energy on quantum level.
[edit] First Principle in Engineering
First Principle in Engineering is the most primitive level where the relationship between function, behaviour and structure can be described using physical laws of nature.
Engineering First Principles can also be associated with the process or method by which an engineering problem is approached. Development teams will often attempt to solve a problem by compiling data or assumptions in ways that are misleading, if not completely erroneous. This leads them down the path of attempting solutions with no hope of success. A classic example is the multiple attempts throughout history to develop a perpetual motion machine. With the application of Engineering First Principles it would be clearly understood that perpetual motion is impossible, no matter how titillating data may appear to suggest otherwise. Engineering First Principles ensures that the physics associated with any problem is soundly understood from the most basic component or aspect of a design, and the solution is built from that point.
