436. And they had breastplates like breastplates of iron. (9:9) This symbolically means that their arguments based on fallacies, with which they battled and prevailed, appeared to them too strong to be refuted.

Breastplates symbolize protections, because they protect the breast. Here they symbolize protections of falsities, which are concocted by arguments based on fallacies, which people use to defend a false proposition. For from a false proposition nothing but falsities can flow. If truths are advanced, they are regarded only externally or superficially, thus also sensually, and so are falsified, becoming then fallacies in the people who entertain them.

Breastplates have this symbolism because battles in the Word symbolize spiritual battles, and weapons of war therefore symbolize various defenses connected with such a battle - as in Jeremiah,

Harness the horses, and mount up, you horsemen! And station yourselves in your helmets, polish the spears, put on the cuirass. (Jeremiah 46:4)

In Isaiah,

He put on righteousness as a breastplate, and a helmet of salvation on His head. (Isaiah 59:17)

In the book of Psalms,

...under His wings you shall be confident; His truth shall be your shield and buckler. (Psalms 91:4)

And so also elsewhere, as Ezekiel 23:24; 38:4; 39:9, Nahum 2:3, Psalm. 5:12; 35:2-3.

Their breastplates being breastplates of iron means, symbolically, that their arguments seemed to them too strong to be refuted; for owing to its hardness iron symbolizes strength.

Intellectual things -- ideas, knowledge, facts, even insight and understanding -- are more separate and free-standing than emotional things, and it's easier to imagine numbering them as individual things. Our loves and affections tend to be more amorphous -- they can certainly be powerful, but would be harder to measure. Using words like “much,” “many,” myriad” and “multitude” to describe a collection of things gives the sense that there is an exact number, even if we don't know what it is and don't want to bother trying to count. These words, then, are used in the Bible in reference to intellectual things -- our thoughts, knowledge and concepts. Words that indicate largeness without the idea of number -- “great” is a common one -- generally refer to loves, affections and the desire for good. Here's one way to think about this: Say you want to take some food to a friend who just had a baby. That's a desire for good (assuming you're doing it from genuinely good motives). To actually do it, though, takes dozens of thoughts, ideas, facts and knowledges. What does she like to eat? What do you have to cook? What do you cook well? Can you keep it hot getting to her house? Is it nutritious? Does she have any allergies? So one good desire can bring a multitude of ideas into play.