Synthesis is complementary to analysis.
Analysis takes something apart to looks at its constituent parts. This can be helpful for understanding and attending to each element separately.
Synthesis puts the elements together and gets them to integrate, harmonise, so that you can move forward in a whole-hearted
You've heard the expression 'the right hand doesn't know what the left hand is doing'. This is an apt description for how we sometimes function inside, as well. Think of any complicated decision you're trying to make:
one bit of you is counselling going one way, and another bit of you would rather go a different way. However much you try to argue it out, reaching agreement is often far from obvious. This is where the powerful approach of Psychosynthesis can really help.