Listen to this morning's class on Derekh HaShem here.
Follow along with the sources here.
For further research:
1) Read our devar Torah for Parashot Matot/Masei, related to the final concept that we discussed, here.
2) Read Melila Hellner-Eshed's brief discussion of Zohar's concept of "turning darkness into light," in A River Flows From Eden, here.