To be honest I know very little about m&p apart from the fact that you can buy it in different types - such as goats milk base or 'clear' base etc and then literally melt and pour and use it next day. Unlike Cold Process (which is the traditional method using Lye) that need a curing period of about 4 weeks.
The bar of soap you have in your drawer will have been made in a factory and although its Simple soap you will find that the ingredients that have been used to make it are anything but simple. In fact I've gone to the Simple site and the ingredients are
Aqua, (ok so water to start the whole process of with the caustic soda)
Etidronic Acid, (an agent added to swimming pool chemicals to inhibit stains it is also added to bleach!)
Glycerin,(lovely and moisturising but why are they adding it? glycerin SHOULD be a natural by product of natural soap)
Sodium Chloride,(salt to 'help' bond the fatty acids and keep the soap firmer)
Sodium Cocoate, (this is just saponified coconut oil - coconut oil being a firm favourite with soap makers as it makes gorgeous bubbles/lather and can help with skin problems. )
Sodium Palm Kernelate,(saponified name for palm kernel oil. THe more palm oil we use, the less orang-utans will survive
SImple have NOT stated that this is from a sustainable source. from this we have to deduce it is not)
Sodium Tallowate, (saponified Lard! beef fat)
Tetrasodium EDTA (artificial preservative . some concerns as to whether this agent has low to moderate risk of causing cancer)
Now - the Knights Castile - I'm not sure what KNights use as if they are a large manufacturer then some preservatives might have to creep in to keep the large customer base happy but..the average castile is
olive oil, lye, water.
The lye saponifies the ingredients so you get 'aqua, sodium olivate' and that's it I believe!
my own ingredients are -
Sodium Olivate (saponified olive oil)
Sodium Cocoate (saponified coconut oil)
goats milk
In a nutshell I think what Kitty Little is trying to say is that use a castille to get a perfectly natural product
by adding shea butter you are 'superfatting' as shea will not saponify and it will keep its beautifully moisturising properties. geranium is my best seller currently so you will be on a winner with any soap with that in I do believe lol!!
good luck!! have fun