The secret things are those not yet revealed.  The glorious secret that had not been revealed to the Israelites is that the Law would be fulfilled in Christ Jesus and that there would be a return to Grace. -> Not just Grace as it was with Adam and Abraham and everyone up to the giving of the Law. -> But Grace that enabled man to become a NewCreature<p> The lot for Israel was to do the Law and their agreement to the terms of the Law would be binding until that glorious secret would be revealed.