All things that exist have an identity – they are what they are, and are not what they are not.  Although this sounds obvious, almost foolishly obvious, it is both the fundamental principle of metaphysics, and the fundamental principle of epistemology: A is A.  Separate observers of a single thing may see different aspects of the thing, but the thing itself remains one existing thing, with a single identity.  Consider a sticky lying in my yard.  To my son it is a walking stick, to my daughter, a toy for the dog to fetch, to me, firewood.  But all of these very different descriptions are derived from the properties of the stick as a stick.  There is no fundamental disagreement between these descriptions – our knowledge of the stick does not conflict – nor do the properties that they rely upon (strength, size and weight, flammability) conflict.

Every existing thing at any point in time has a set of properties.  The relationships between existing things – how they interact, forces acting between them, relative positions, relative values of their common properties – are also constant and consistent at any point in time, and will therefore change over time in only the way in which they shall change.  There is no arbitrariness in how a system of interacting things evolves over time, no true randomness, no possibility of following different paths from a single starting condition.  This fact is the law of cause and effect – every change in the state of a thing has a cause, and every set of identical causes creates a single effect.  If a set of things is placed in the same condition with the same influences acting upon them at two different times all else being the same, they will evolve identically both times.  This principle of a thing – that it will act consistently when starting from the same condition and relation to other objects – is the nature of a thing.  All things have a nature.  The issue of free will – an axiomatic property solely (to our knowledge) of human beings, we have discussed elsewhere.

The statement that things have a nature is equivalent to stating that things must follow natural laws.  The existence of these laws is based upon the very principle of cause and effect.  To have effects, there must be causes, and as stated previously, the same effect will follow the same starting condition within a system of interacting things.  The next key question is how does Man come to understand these natural laws?

Here is a very short outline of Ayn Rand’s theory of epistemology.  Man’s understanding of the Universe begins with observation of the identity of things, and grasping the commonality between individual things of the same category.  Each category is then identified with a concept, in which the actual values – measurements – of the essential defining properties of the individuals within the category are removed, along with any non-essential variations between individuals.  Interactions and relationships between existing things are similarly observed, and similarly abstracted into generalizations, again omitting the non-essential details and magnitudes of the interactions.  The fundamental building blocks of human knowledge, then, are concepts and generalizations.  These form the basis of a hierarchy of concepts and generalizations, as commonalities can be found between first level concepts (the classic example being tables, chairs, beds) to form a broader categorization and associated concept (furniture).  Generalizations are structured into a similar hierarchy (animals are attracted to the center of the Earth, furniture is attracted to the center of the Earth,…, all physical objects close to Earth are attracted to the center of Earth, …, all physical objects are attracted to all other physical objects).

At the top of the hierarchy of generalizations related to the behavior of the physical world lie the Laws of Nature as understood by Man.  Here we need to note several points.  If (and only if) the process of generalization has been performed solely through the use of observation and the rigid application of logic, without introducing arbitrary preconditions and assumptions, Man’s understanding of the Laws of Nature is correct at every level of development, though not generally complete.  For example, Newtonian mechanics is correct for phenomena not involving speeds approaching the speed of light, sizes approaching the size of an atom, or masses approaching the mass of the Sun.  Einstein’s dynamics do not replace Newtonian physics, it includes it and expands upon the realm to which physics applies.  Secondly, there is a distinction between the existence of natural laws, which is a metaphysical statement independent of the existence of a mind to comprehend them, and Man’s scientific theories describing these natural laws, which by definition rely upon the existence of human minds, and are obviously the product of human epistemology.

We are finally in a position to answer the question – Must the Universe be Simple?  Simplicity is itself a human concept – there is no meaning to “simplicity” outside a human brain.  Man’s approach to understanding the Universe is a continual process of exploration, observation, concept formation, generalization, theorizing and theory verification through more observation.  Every step of this process necessarily involves simplification by omitting the measurements of the properties of the items being further abstracted.  This simplification is required by the finite human brain in order to be able to comprehend and reason at an ever increasing level of abstraction.  Man continually quests for higher and higher levels of comprehension of the Universe, creating the epistemological tools for this grand quest in the form of higher levels of abstract mathematics, which he then uses to further simplify the description of the Universe in the form of advanced physics.  (At least, this is how science is supposed to progress, though modern physics has attempted to find inappropriate short cuts to knowledge).

The answer, then, is that yes, the Universe must be simple.  For simplicity is a purely human concept, and our understanding of the Universe is based upon a continual process of simplification.  Another way to put this is that there is no meaning in a Universe that is incomprehensibly complicated, and to be comprehended, the Universe must be simple.  One cannot make the assumption that the Universe is too complicated to be understood and progress at all toward its understanding, and yet we are surrounded by evidence indicating very clearly that we do have a very good comprehension of our Universe.  Human technology could not exist otherwise.