A tangent is a line that intersects a curve at some point where the slope (angle) of the line and the curve are equal, and continues on in either direction, away from the curve forever if that curve is part of a circle. That's why when people talk about going off on a tangent, it means they're heading off topic, and at some point they'll have admit they've digressed (usually by saying 'but I digress') and turn back around in order to stay the true course (this is all common knowledge, yes, but why not start simple). Now, let's imagine that when we talk on a subject, in conversation or in debate or in lecture, that the substance of the subject comprises the volume of a cone. A cone is a three-dimensional shape that's comprised of a great many circles that get smaller and smaller as they move up a line (the cone's height), eventually arriving at a point. Let's say that arriving at this point is the ultimate goal of any purposeful discussion, and we get there by working our way up the concentrically shrinking/rising circles. We always start on a point along any given circle's circumference (it's perimeter), and if it's a new(ish) topic, we're generally starting at the base of the cone. As we take wind and start to speak, we can move the conversation in a number of ways. I'd say the most common way is to tarry along the circumfence of the circle, until a point (not THE point, but a point - there are a kajiliion of them on every plane; the surface of the cone is a plane) is made that belongs on a higher level and elevates the conversation to a higher ring. We then continue along this ring until that happens again, and this is how we elevate the conversation. The conversation could continue entirely along the surface of the cone and eventually reach THE point without ever heading towards the center of the cone, where deep conversations take place, and I'll tell you why that's a tough place to be in a minute. This type of upward-spiralling circumferential discussion, I would posit, is a healthy discussion, as discussions almost always take place in a circular fashion, and thus require the path of circumference to keep them moving. My case is that a circular discussion is never a bad thing, but it wanes when you make it all the way round and discover it hasn't moved upward (as you may see, you can make it almost all the way around a circle and still keep from taunting futility if you're able to gain a touch of higher ground before you close the gap on any given ring; and since there are a seemingly infinite amount of rings that make up your topic cone, it really doesn't take much more than a small step to keep you moving in a positive direction). Up and up and round and round we travel, until we reach the summit, plant our flag of reason on it's verbose perch, and ramble on along our new learned level of understanding to find another topic to conquer. Yes, this is a precipitous place to be, at the height of conversation, but there are many cones to climb.
So, you'd like to get off the circular surface of a topic (it can get dizzying) and plod through it's skin to taste it's sweet innards? Well, you're in for a treat, as they taste pretty good, but they don't provide you with much direction. You can crawl into the voluminous expanses of a topic's substance and become lost forever - to take a linear approach to a conversation is to behave in such an efficient manner that it's almost beyond human capability, but should you succeed in going the straight and narrow, there are these items to which you ought to pay heed: Your direction - are you headed along a radial path, or are you cruising along a chord (see circle diagram. A chord is a straight line between any two points on a circle's circumference). And if you're on a chord, well then you're going to come shooting right out the other side of the mountain at some point, and you'd better know it, otherwise you're doing no better than the man on a tangent. If you stop at any point during your linear journey to the center of argument, then what? You'll be terribly hard-pressed heading straight up - like making your way to the tip of an iceberg by digging a long tunnel and then chipping away at it's ceiling - there's a lot of topical weight bearing down on that central matter; it's a heavy place. And, if you decide to stay where you are and start in a circle again, well then you may do so, but you've created a new surface for yourself and the slope is much steeper, or THE point is of a lesser quality of air (see diagram). Mining your topic is bound to get you into trouble, but it's one hell of a trip. The nice part is that you shouldn't have much trouble retracing your steps if the canary quits chirping. I hope you can see why deep conversations rarely get to THE point, although they are rewarding in the sense that thay offer overwhelming perpsectives and provide plenty of mindful exercise.
Consider these notions next time to set off to find purchase on a greater topical slope among the foothills of small talk and idle banter (Ide banter isn't even a foothill - it's the Nebraska of conference, where you're apt to dig a trench in order to climb a hill. But hey, the corn is sweeter than candy, and there's plenty of room for all). Also, consider that I may have just wasted a hunk of your time if you don't take adsurdity seriously.