Guide for the Perplexed, by Moses Maimonides, Friedländer tr. , at sacred-texts.com
Ruaḥ is a homonym, signifying "air," that is, one of the four elements. Comp. "And the air of God moved" (Gen. i. 2).
It denotes also, "wind." Comp. "And the east wind (ruaḥ) brought the locusts" (Exod. x. 13); "west wind" (ruaḥ) (ib. 19). In this sense the word occurs frequently.
Next, it signifies "breath." Comp. "A breath (ruaḥ) that passeth away, and does not come again" (Ps. lxxviii. 39); "wherein is the breath (ruaḥ) of life" (Gen. vii. 15).
It signifies also that which remains of man after his death, and is not subject to destruction. Comp. "And the spirit (ruaḥ) shall return unto God who gave it" (Eccles. xii. 7).
Another signification of this word is "the divine inspiration of the prophets whereby they prophesy"--as we shall explain, when speaking on prophecy, as far as it is opportune to discuss this subject in a treatise like this.--Comp. "And I will take of the spirit (ruaḥ) which is upon thee, and will put it upon them" (Num. xi. 17); "And it came to pass, when the spirit (ruaḥ) rested upon them" (ib. 25); "The spirit (ruaḥ) of the Lord spake by me" (2 Sam. xxiii. 2). The term is frequently used in this sense.
The meaning of "intention," "will," is likewise contained in the word ruaḥ. Comp. "A fool uttereth all his spirit" (ruaḥ) (Prov. xxix. 11), i.e., his intention and will; "And the spirit (ruaḥ) of Egypt shall fail in the midst thereof, and I will destroy the counsel thereof" (Isa. xix. 3), i.e., her intentions will be frustrated, and her plans will be obscured; "Who has comprehended the spirit (ruaḥ) of the Lord, or who is familiar with his counsel that he may tell us?" (Isa. xl. 13), i.e., Who knows the order fixed by His will, or perceives the system of His Providence in the existing world, that he may tell us? as we shall explain in the chapters in which we shall speak on Providence.
Thus the Hebrew ruaḥ when used in reference to God, has generally the fifth signification: sometimes, however, as explained above, the last signification, viz., "will." The meaning of the word in each individual case is therefore to be determined by the context.