While trying to modify as little as possible, how can I make the bilateral sales contract in Practical Example 1 unilateral?
What if I copy and paste Practical Example 2 and modify like it this?
Daniel[Alex] offers (or promises) a free watch[a bicycle] to anyone who three tokens from the packets of cereal he manufactures, together with a cheque for £5[pays him £150].
But then doesn't my edit become a bilateral contract?
Poole, Shaw-Mellors. Contract Law Concentrate (4 ed 2019). p 5.
The key distinction: bilateral and unilateral agreements
Broadly, agreements will be one of two types: • bilateral • unilateral.
Bilateral agreements: by far the most common in practice and consist of a promise in exchange for a promise. Bilateral means both parties are bound on the exchange of promises, although there has yet to be any performance of those promises.
A typical sale of goods agreement is bilateral.
Practical example 1
Alex offers (or promises) to sell his bicycle to Becky for £150 and Becky accepts, thereby promising to pay £150. (We will use this as our example of a bilateral agreement and look at variations and additions to the facts throughout this chapter.)
Unilateral agreements: consist of a promise in exchange for an act. It follows that only one party is bound at the outset by a promise. The other’s acceptance is the performance of the requested act.
For example, a typical unilateral agreement will involve an offer of a reward and may be phrased as an ‘if’ contract: I promise to pay £50 to anyone who finds and returns my lost dog.
Practical example 2
Daniel offers (or promises) a free watch to anyone who returns three tokens from the packets of cereal he manufactures, together with a cheque for £5. Emily accepts by returning the three tokens with her cheque for £5. (We will use this as our example of a unilateral agreement and return to this example later in the chapter.)
Making the correct distinction.
It is not possible to accept a unilateral offer by promising to find and return the lost dog or by promising to collect and return the tokens and the cheque. By comparison, the agreement to sell the bicycle cannot be unilateral. Students sometimes suggest that a simple sale contract is unilateral by interpreting the act of paying for the bicycle as the requested act. This is incorrect since, as long as it is possible to accept by promising to buy (which it is in the example), the agreement will be bilateral.