Liquidity is the key, in my opinion, to distingusihing between investment and speculation - the source of the liquidity.

If we are relying upon the contract and for example collecting the coupons and principal of a bond, the source of liquidity is the obligor under the contract. If we are relying upon sale of the asset in a market, this is speculation. We are, after all, uncertain that the market may exist or that the price will prove satisfactory.

This also delivers a time dimension and shades of grey between these - in general the longer we hold an asset the more income is non-market.

I have written a number of articles in the past year on this - happy to send them to anyone who would like to read them - drop me an email at: [email protected]