The "higher decree" is God foreknowledge of all events, we agree. Pilgrim, consider another way of looking at what Christ did for us from Dr. John W. McCormick:

Heb. 4:15: Our Lord was subjected to testing in the totality of His Being, not that He might “overcome temptation and thus win a victory for all His redeemed”, but in order that the Impeccability of His Person should be forever manifested to men, to angels, and to demons! There is every reason to believe that Satan would have gladly avoided the encounter with the Lord Jesus Christ if he could have received Divine permission to do so; for he well knew that the inevitable result of that meeting was going to be a humiliating defeat for himself and for his kingdom of darkness. It was then (at the Temptation in the Wilderness) that our Lord entered into the strong-man’s house, and bound the strong man hand and foot. After that He went to the cross and “spoiled the strong man’s goods” for ever! (Matt. 12:29; Mark 3:27). Thus, the Temptation of Christ was not a matter of laying the redemptive purpose of God on the block; but it was an annunciation to men, to angels, and to demons that King Jesus had come to dethrone the usurper (Satan), to smash his kingdom into eternal oblivion, and to restore His crown rights to every one of His beloved ones who were yet to be drawn to Him in repentance and faith. To put it another way, it was nothing short of a declaration of total and all-out war! And there was never any question as to the outcome!
Geomic