"Heaven and Earth, that is Tao"

In the first chapter of The Great Treatise we find:

The changes and transformations of Heaven are in the symbols of Change
The changes and transformations of Earth are in the forms of Change

Also:

What moves and completes the symbols is called Ch'ien.
What unfolds them into patterns of living is called K'un.

Thus, Ch'ien represents enfolded or implicate order, creative, symbolic reality; while K'un is explicated/unfolded, structive, formative reality.

Earth (K'un) is represented by the form of the simple square. 

Heaven (Ch'ien) is immaterial or intangible and has no form as such, but we may represent it through an overlaid series of lines that partition the square into four discrete regions:

The resulting figure can be resolved into fractions of sixteen.  The respective areas of the four discrete regions are 1/16, 3/16, 5/16, and 7/16, comprising a unity.  These four fractions are identical to the probabilities, given by the yarrow oracle, of measuring the four xiang symbols during divination.  

Having received the four symbols by combining Heaven and Earth, we project them onto our figure, yielding a full field to support the existence of the 64 Images:
  

From this we can infer that the  Eight Diagrams emerge from the 64 Images, consistent with Dr. Stephen Karcher's argument that the 64 Images "preceded" the Eight Diagrams (Ba Gua), which are used for identification and interpretation of the Images.

The ancients are said to have devised many implements by imitating Change.  Here, and elsewhere, I suggest that that the yarrow oracle was devised to imitate the intermingling of Heaven and Earth that reveals the xiang.  The figures presented here are purely geometric, hence they are antecedent of human artifice.  The xiang are eternal; coeval with, and fairly indistinct or inseparable from Change.  The ancient sages' far-reaching powers of sentience and cognition brought forth the xiang into consensus reality for the use of mankind.

The point that I hope to have made is that the xiang are entangled with Change, embedded or encoded in Change by way of this intermingling of the square (representing Earth) and the enfoldment that Heaven represents.  Without the enfoldment, we cannot discern the symbols in the square; without the square, the symbols have no basis for existence.  Indeed, "Heaven and Earth, that is Tao."

If we accept this line of reasoning, we can posit a natural, mathematical interpretation for Change that can be extended with further investigation.