capacitance - Is a human (or other) electrical signal absolutely necessary to activate a capacitive touchscreen?

I know this is the general wisdom, and that someone has asked a similar question here: How can a capacitive touch screen be triggered without human contact?

However, I didn't quite understand the conclusion that by simply grounding e.g. A carrot or stylus, or connecting them to a conductive plate, this would be enough to allow them to activate the touchscreen. Is the idea that the ground or conductive plate pick up enough electricity in the environment that they can act as a substitute for a human?

As a related note, I held a stylus through many layers of folded up, thick woollen sweater, and it was still able to activate the touchscreen. Was my body's electrical signal definitely conducted through the sweater?

Apologies if my question sounds a bit ignorant. I am not an electrician, but I understand the basics of electrical circuitry and how capacitors work. The iPhone's capacitive touchscreen nevertheless seems like a bit of a black box to me.

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Thank you all. Based on your responses and my reading of the Q&A referenced by @gbarry, my understanding of this is now almost complete. There remainas these issues that I am unclear on:

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  It seems that it is a very common misconception, then, that it is a body's electrical signal (current) that is necessary to activate the iPhone touchscren in particular. Rather, what is sensed by the electrodes of the touchscreen circuit is either insulation or capacitive coupling, but supposedly not conductivity. Since I always considered insulation and conductivity as belonging on the same scale, could someone perhaps clear this up for me, while illuminating whether or not this is what is meant here by "capacitive coupling"?

  
  


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  I have understood that large surface area is often an important determinant of capacitive coupling. Is this the only reason that it is suggested the contacting body be grounded, or is it necessary for another reason, e.g., To "complete the circuit" initiated by the iPhone?

  
  

I'll gladly award the bounty to whomever can answer these questions in a way that I can understand! Thank you again.