Following the leads in the wonderful responses of the contributors here, I believe the following interpretations of the symbolism in this picture are probably correct.
These two figures are most likely Ecclesia (sitting) and Synagoga (prone) with science linked to Ecclesia and therefore enlightenment and triumph over those who blind themselves to the truth. A monstrance, palm frond, a blindfolded figure, and fruit --all depicted in this picture--can be found in Reuben's tapestry The Triumph of the Eucharist, discussed in Tapestry of the Baroque: Threads of Splendor on pg. 219.
Each figure and item is symbolic:
I believe the "cloud" is actually a whirlwind (the foot of God) related to the passage in the Bible Jeremiah 23:19 as discussed by Ritenbaugh : He is talking about a tornado that He has sent—a violent windstorm. The false prophets have said, "No bad is coming" (verse 17). God says, "Do they ever listen to Me? I've said, 'I'm sending a whirlwind, and it's going to fall on the heads of the wicked.' How dare they say that everything is going to be okay!"
The palm branch in Ecclesia's hand is a symbol of victory as explained in this Wiki.
The branch in Synagoga's hand most likely represents a pruned branch of ivy (ivy is depicted just above Synagoga), related to John 15:6: "If a person does not dwell in Me, he is thrown out like a [broken-off] branch, and withers ... . " The cut branch symbolizes in the Bible those pruned from the ivy, representing Christ, who don't bear fruit because they don't accept Christ and are therefore cut or broken off the ivy.
The three objects on a book on the ground could very well be fruit with the implication that the sciences as well as faith bear fruit. That would also explain what looks suspiciuosly like a pineapple in the lower left. The symbolism behind pineapples is explained here.
And, don't forget the symbolism behind the right side (dexter) and the left side (sinister) in religious themes that are also reflected in this image.
The seashell(s?) in the lower left corner might be associated to St. James, pilgrimage, and the light showing the way (read the section on the Enlightenment Era in the Wiki on The Way of St. James). Riccati's first name Jacopo is derived from the Latin Iacōbus as is James.