How to change size of system font(s)?

[Richard Owlett <rowlett@cloud85.net>]

The default font in Squeeze(Gnome2) and Jessie(Mate) is too small!
Gedit and Pluma allow changing from default size of "10"[units 
not specified]. I find setting to 14 or larger much more legible 
on my laptop.

Other programs, e.g. Synaptic, give no option to chose an 
acceptable font size.

Is there any way to force a minimum font size system wide?
Can it be preseeded on installation?

TIA