Mutability is absolutely inconsistent with simplicity, whether the change come from an internal or external principle. If a change be wrought by something without, it supposeth either contrary or various parts in the thing so changed, whereof it doth consist; if it be wrought by anything within, it supposeth that the thing so changed doth consist of one part that doth change it, and another part that is changed, and so it would not be a simple being. If God could be changed by anything within himself, all in God would not be God; his essence would depend upon some parts, whereof some would be superior to others. If one part were able to change or destroy another, that which doth change would be God, that which is changed would not be God; so God would be made up of a deity and a non-deity, and part of God would depend upon God; part would be dependent, and part would be independent; part would be mutable, part immutable; so that mutability is against the notion of God’s independency as well as his simplicity.* God is the most simple being; for that which is first in nature, having nothing beyond it, cannot by any means be thought to be compounded; for whatsoever is so depends upon the parts whereof it is compounded, and so is not the first being. Now God being infinitely simple, hath nothing in himself which is not himself, and therefore cannot will any change in himself, he being his own essence and existence.

Charnock, S. (1864–1866). The Complete Works of Stephen Charnock (Vol. 1, pp. 393–394). Edinburgh; London; Dublin: James Nichol; James Nisbet and Co.; W. Robertson; G. Herbert.